diff --git a/.agents/skills/writing-docs/SKILL.md b/.agents/skills/writing-docs/SKILL.md
index 0e393cfcc8..8950cd7ec8 100644
--- a/.agents/skills/writing-docs/SKILL.md
+++ b/.agents/skills/writing-docs/SKILL.md
@@ -47,8 +47,13 @@ what a reader must act on; drop the before-picture.
 * Changed in v11: `stringOutput()` always returns a `str`, never None.
 * Changed in v11: emits `\tuplet`; the arguments are now actual, normal.
 * New in v11.
+* Deprecated in v11: use `.octave`, which is now always an int.
 ```
 
+A deprecated function or method also gets `@common.deprecated(...)`. A property
+gets only the marker, since IDEs read every property while inspecting an object;
+leave `# Add real deprecation message here in vX` in its body instead.
+
 A plain bug fix — code now does what it always claimed — gets no marker and no
 doctest. It goes in the commit message.
 
diff --git a/AGENTS.md b/AGENTS.md
index 6b9738c6f2..2e7640dcab 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -29,6 +29,10 @@
   `environLocal.printDebug(...)`, or `environLocal.warn(...)` when the user should hear
   about it every time. `test/toggleDebug.py` switches debug output on and off.
 - New exceptions subclass `exceptions21.Music21Exception`.
+- Deprecate a function or method with `@common.deprecated(...)`. Never put it on a
+  property: IDEs read every property while inspecting an object, so the warning would
+  fire on people who never used it. For a property, write `* Deprecated in vX: use Y.`
+  in the docstring and leave `# Add real deprecation message here in vY` in the body.
 - Return named things — a small class, a `namedtuple`, a dict — never a positional tuple of more than 2 (maybe 3) elements
   whose elements each mean something different and unrelated (x, y, z is okay for instance). Nobody should write `returned[3][0][7]`.
 - Don't reuse a variable name once the type of what it holds changes
@@ -128,6 +132,12 @@
   after addressing the problem.  (A blind close or close with "not accepted" etc. generally means that the issue/PR
   has too many problems to easily solve and has become a burden for the maintainer).
 - Do not include a "Tests run" section unless the testing procedure was unusual (like it affects part of the system without standard tests, like the testing system itself.)
+- While someone is reviewing a PR or a pushed branch, "do X" is not "commit and push X":
+  make the change and leave it unstaged. When the list looks finished (or you hear "done!"
+  or "push it"), offer to commit, or to commit and push. Batch a round's small fixes into
+  one commit; no micro-commit trains. Prefer new commits to amend + force-push, since the
+  reviewer may have pulled the branch; if asked to fold a fix into the commit it changes,
+  amend, force-push with `--force-with-lease` against an explicit SHA, and say so.
 
 # Writing style
 
diff --git a/documentation/source/about/index.rst b/documentation/source/about/index.rst
index ee319489b2..d0be870496 100644
--- a/documentation/source/about/index.rst
+++ b/documentation/source/about/index.rst
@@ -8,4 +8,5 @@ About `music21`
    about
    applications
    faq
+   migratingToV11
    referenceCorpus
diff --git a/documentation/source/about/migratingToV11.rst b/documentation/source/about/migratingToV11.rst
new file mode 100644
index 0000000000..acc455dfde
--- /dev/null
+++ b/documentation/source/about/migratingToV11.rst
@@ -0,0 +1,268 @@
+.. _migratingToV11:
+
+Migrating to music21 v11
+========================
+
+*(This is an in-progress guide that was automatically generated by Myke's AI Agent.)*
+
+What changed between the v10 line and v11, and what to use instead.  The big, code-breaking items come first, then smaller
+improvements by area, then one table of everything removed or deprecated.
+
+
+Python 3.12 or newer
+--------------------
+
+Python 3.11 support is gone; 3.12, 3.13, and 3.14 are tested.  The payoff is
+real generics: ``Stream`` and its iterators use the PEP 695 bracket form, so a
+type checker can follow ``stream.Stream[note.Note]()`` all the way to
+``for n in s: n.pitch``.
+
+
+Octaves are always integers
+---------------------------
+
+**In one line:** ``octave`` is always an ``int``, and ``octaveIsImplicit`` says whether you gave one.
+
+Before v11, ``pitch.Pitch('F#').octave`` was ``None``: a lovely idea (an
+F-sharp in *any* octave) that crashed the moment someone wrote
+``p.octave + 1``.  The pitch knew all along which octave it would use for
+MIDI or a staff.  It kept that in ``implicitOctave``, a property that nobody
+remembered.  Now ``octave`` does that job itself:
+
+>>> from music21 import *
+>>> anyFSharp = pitch.Pitch('F#')
+>>> anyFSharp.octave
+4
+>>> anyFSharp.octaveIsImplicit
+True
+
+Nothing else about an octave-less pitch changes.  It still prints without a
+number, transposes without one, and is not equal to an explicit F#4:
+
+>>> anyFSharp
+<music21.pitch.Pitch F#>
+>>> anyFSharp.transpose('P8')
+<music21.pitch.Pitch F#>
+>>> anyFSharp == pitch.Pitch('F#4')
+False
+
+Give it an octave and the flag flips:
+
+>>> anyFSharp.octave = 5
+>>> anyFSharp.octaveIsImplicit
+False
+>>> anyFSharp
+<music21.pitch.Pitch F#5>
+
+Notes follow along: ``note.Note('B-').octave`` is ``4``, and the flag lives
+on the note's pitch, ``n.pitch.octaveIsImplicit``.
+
+.. list-table::
+   :header-rows: 1
+   :widths: 50 50
+
+   * - Before v11
+     - v11
+   * - ``if p.octave is None:``
+     - ``if p.octaveIsImplicit:``
+   * - ``p.octave = None``
+     - ``p.octaveIsImplicit = True``  (the old spelling is deprecated; removed in v13)
+   * - ``p.implicitOctave``
+     - ``p.octave``
+   * - ``if p.octave is None: p.octave = p.implicitOctave``
+     - ``p.octaveIsImplicit = False``
+   * - ``octave: int | None``
+     - ``octave: int``
+
+``p.octave + 1`` and ``f'{p.name}{p.octave}'`` no longer crash.  The few
+methods that need a pitch's *own* octave, such as
+:meth:`~music21.pitch.Pitch.transposeAboveTarget`, still raise for an
+implicit one; set ``.octave`` first.  ``implicitOctave`` stays as a synonym
+so nothing breaks today, but it is deprecated and starts warning in v12.
+
+
+KeySignature.sharps is always an int
+------------------------------------
+
+Similar idea to Octave.  ``KeySignature.sharps`` (and ``Key.sharps``) is an
+``int`` you can add to and subtract from.  A non-traditional signature is a
+flag plus a list of pitches.  ``sharps=None`` still works but warns:
+
+>>> unusual = key.KeySignature()
+>>> unusual.isNonTraditional = True
+>>> unusual.alteredPitches = ['E-', 'G#4']
+>>> unusual
+<music21.key.KeySignature of pitches: [E-, G#4]>
+
+
+Chord indexing gets simpler
+---------------------------
+
+``c[1]``, ``c['G4']`` and ``c[somePitch]`` still return the chord's
+:class:`~music21.note.Note`; everything fancier is gone.  Attribute paths
+such as ``c['2.tie']`` and ``c['D-4.style.color']`` no longer work, a Note is
+no longer accepted as a key (use its pitch), and the per-note getters and
+setters (``getTie``, ``setColor``, ``getNotehead``, and their siblings) are
+deprecated.  Index, then use the Note:
+
+>>> c = chord.Chord('C4 E4 G4')
+>>> c['E4'].tie = tie.Tie('start')
+>>> c[1].tie
+<music21.tie.Tie start>
+
+
+VoiceLeadingQuartet needs its four notes
+----------------------------------------
+
+``voiceLeading.VoiceLeadingQuartet(v1n1, v1n2, v2n1, v2n2)`` requires all
+four notes up front, the first Music21Object ever to insist on arguments.  In
+return they are always Notes, never ``None``.  ``analyticKey`` is now
+``key``, ``vIntervals`` and ``hIntervals`` are tuples, and two dogmatic names
+got truer ones: ``opensIncorrectly()`` is ``not modalOpening()`` and
+``closesIncorrectly()`` is ``not clausulaVera()``.
+
+
+Roman numerals
+--------------
+
+* ``romanNumeralFromChord`` keeps the sharp on major-quality chords built on
+  the raised sixth and seventh degrees in minor: ``#VI``, not ``VI#63``.
+  ``correctRNAlterationForMinor`` gained a ``chordHasMajorThird`` keyword for
+  the same reason.
+* Figures containing ``x``, ``y`` or ``z`` raise.  ``RomanNumeral('IIIx')``
+  used to be a III13 chord by accident.
+* ``FigureTuple`` and ``PitchFigureTuple`` are typed NamedTuples, and
+  ``FigureTuple.fromPitchAndReference()`` replaces ``figureTupleSolo``.
+
+
+Durations and sorting
+---------------------
+
+* Two Durations with ``expressionIsInferred`` True are equal when their
+  quarterLengths match; type, dots and tuplets are free to be re-expressed.
+* ``sorting.SortTuple`` is a modern NamedTuple.  ``priority`` and
+  ``classSortOrder`` may be floats, and ``modify()`` with a bad field name
+  raises ``ValueError``.
+* tinyNotation's undocumented ``0`` duration (a whole bar plus a fermata) is
+  deprecated.
+
+
+Streams
+-------
+
+* New ``Stream.isAtEnd(el)`` says whether ``storeAtEnd`` put ``el`` there.
+* ``Stream.hasElement(el)`` is removed: write ``el in s``.
+  ``hasElementOfClass`` is deprecated: write ``if s.getElementsByClass(X):``.
+
+
+Pitches
+-------
+
+``pitch.simplifyMultipleEnharmonics`` takes ``criterion`` and ``keyContext``
+as keyword-only arguments.
+
+
+File formats
+------------
+
+* **ABC**: ``w:`` lyric lines are imported, with hyphenation and ``*`` skips.
+  ``abcToStreamOpus`` always returns an Opus.
+* **Humdrum**: grace notes keep their written duration instead of becoming
+  eighths; duration parsing lives in a new ``hdStringToDuration``; a token
+  with no duration warns when a quarter is assumed; ``GlobalReference`` is no
+  longer a Music21Object.
+* **LilyPond**: output targets current LilyPond (``\tuplet``, modern barline
+  names, ``\markuplist``), and every ``stringOutput()`` returns a ``str``.
+* **MIDI**: ``midiEventsToInstrument`` is removed; use
+  ``midiEventToInstrument``.
+* **Vexflow**: the ``music21.vexflow`` module is gone.  It had not worked in
+  a decade; music21j is the way to draw in a browser.
+* **configure**: choosing MuseScore as the MusicXML reader also sets
+  ``musescoreDirectPNGPath``.
+
+
+figuredBass, features, tree
+---------------------------
+
+* figuredBass: ``hiddenFifth`` and ``hiddenOctave`` are now ``hiddenFifths``
+  and ``hiddenOctaves``, matching ``parallelFifths``.  ``FiguredBassScale``'s
+  first argument is ``scaleTonic``, not ``scaleValue``.  Rests inside a
+  possibility are typed sentinels rather than the string ``'RT'``.
+* features: ``Feature.vector`` starts as ``[]`` rather than ``None``, and
+  ``FeatureExtractor.dimensions`` defaults to 1.
+* tree: ``ElementTimespan`` and ``PitchedTimespan`` take their arguments in
+  the same order as ``Timespan``; ``offset``, ``endTime`` and ``element`` are
+  required.
+
+
+For developers
+--------------
+
+* Type annotations across nearly the whole library, with ``t.cast()`` for
+  narrowing and ``@property`` decorators throughout.
+* ``common.enums.ContainsEnum`` is not needed: Python 3.12's ``StrEnum``
+  suffices, or ``HexEnum`` for hex values such as MIDI.  The alias leaves in
+  v12.  ``common.defaultlist`` is deprecated.
+* The test runners import modules the normal way, so a module's tests no
+  longer need ``from music21.key import KeySignature`` to compare types.
+* AI agents get their own instructions, skills and shared memory in
+  ``AGENTS.md`` and ``.agents/``.
+
+
+Removed and deprecated
+----------------------
+
+.. list-table:: Removed in v11
+   :header-rows: 1
+   :widths: 50 50
+
+   * - Gone
+     - Use instead
+   * - Python 3.11
+     - Python 3.12 or newer
+   * - ``music21.vexflow``
+     - music21j
+   * - ``midi.translate.midiEventsToInstrument``
+     - ``midiEventToInstrument``
+   * - ``Stream.hasElement(el)``
+     - ``el in s``
+   * - ``musicxml.xmlToM21.MusicXMLImporter.identificationToMetadata``
+     - ``addIdentificationToMetadata``
+   * - a string for ``musicxml.xmlToM21.MeasureParser.getStaffNumber``
+     - an ``int``
+   * - ``VoiceLeadingQuartet.unison`` / ``.fifth`` / ``.octave``
+     - ``interval.Interval('P1')`` and friends
+   * - ``c['2.tie']`` attribute paths into a Chord
+     - ``c[2].tie``
+   * - a Note as a Chord index, ``c[someNote]``
+     - ``c[someNote.pitch]``
+
+.. list-table:: Deprecated in v11 (removed in v12 unless noted)
+   :header-rows: 1
+   :widths: 50 50
+
+   * - Deprecated
+     - Use instead
+   * - ``Stream.hasElementOfClass(X)``
+     - ``if s.getElementsByClass(X):``
+   * - ``Chord.getTie``, ``setTie``, ``getColor``, ``setColor``,
+       ``getNotehead``, ``setNotehead``, ``getNoteheadFill``,
+       ``setNoteheadFill``, ``getStemDirection``, ``setStemDirection``
+     - ``c[i].tie``, ``c[i].style.color``, ``c[i].notehead``,
+       ``c[i].noteheadFill``, ``c[i].stemDirection``
+   * - ``roman.figureTupleSolo``
+     - ``FigureTuple.fromPitchAndReference()``
+   * - ``VoiceLeadingQuartet.opensIncorrectly()`` / ``closesIncorrectly()``
+     - ``not modalOpening()`` / ``not clausulaVera()``
+   * - ``KeySignature(sharps=None)``
+     - ``ks.isNonTraditional = True``
+   * - ``variant.addVariant(replacementDuration=...)``
+     - ``replacementQuarterLength=...``
+   * - ``common.defaultlist``
+     - a ``list`` or a ``dict``
+   * - ``common.enums.ContainsEnum``
+     - not needed: ``enum.StrEnum`` suffices, or ``HexEnum`` for hex values such as MIDI
+   * - tinyNotation ``0`` duration
+     - the duration plus an ``expressions.Fermata``
+   * - ``Pitch.implicitOctave``
+     - ``Pitch.octave``  (warns from v12, removed later)
diff --git a/documentation/source/usersGuide/usersGuide_03_pitches.ipynb b/documentation/source/usersGuide/usersGuide_03_pitches.ipynb
index 2026ffef60..40c4f43f81 100644
--- a/documentation/source/usersGuide/usersGuide_03_pitches.ipynb
+++ b/documentation/source/usersGuide/usersGuide_03_pitches.ipynb
@@ -54,7 +54,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 2,
+   "execution_count": 1,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -85,7 +85,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 3,
+   "execution_count": 2,
    "metadata": {},
    "outputs": [
     {
@@ -94,7 +94,7 @@
        "4"
       ]
      },
-     "execution_count": 3,
+     "execution_count": 2,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -105,7 +105,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 4,
+   "execution_count": 3,
    "metadata": {},
    "outputs": [
     {
@@ -114,7 +114,7 @@
        "10"
       ]
      },
-     "execution_count": 4,
+     "execution_count": 3,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -125,7 +125,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 5,
+   "execution_count": 4,
    "metadata": {},
    "outputs": [
     {
@@ -134,7 +134,7 @@
        "'B-'"
       ]
      },
-     "execution_count": 5,
+     "execution_count": 4,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -145,7 +145,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 6,
+   "execution_count": 5,
    "metadata": {},
    "outputs": [
     {
@@ -154,7 +154,7 @@
        "-1.0"
       ]
      },
-     "execution_count": 6,
+     "execution_count": 5,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -177,7 +177,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 7,
+   "execution_count": 6,
    "metadata": {},
    "outputs": [
     {
@@ -186,7 +186,7 @@
        "'B-4'"
       ]
      },
-     "execution_count": 7,
+     "execution_count": 6,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -197,7 +197,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 8,
+   "execution_count": 7,
    "metadata": {},
    "outputs": [
     {
@@ -206,7 +206,7 @@
        "70"
       ]
      },
-     "execution_count": 8,
+     "execution_count": 7,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -215,6 +215,91 @@
     "p1.midi"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "Leave the octave off and the `Pitch` means \"a B-flat in *any* octave.\"\n",
+    "It prints without a number:"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 8,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "<music21.pitch.Pitch B->"
+      ]
+     },
+     "execution_count": 8,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "anyBFlat = pitch.Pitch('B-')\n",
+    "anyBFlat"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "But `music21` often needs an octave anyhow, to play the pitch or put it\n",
+    "on a staff, so `.octave` still answers with the default, `4` (the octave\n",
+    "of middle C), and `.octaveIsImplicit` remembers that you didn't give one:"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 9,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "4"
+      ]
+     },
+     "execution_count": 9,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "anyBFlat.octave"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 10,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "True"
+      ]
+     },
+     "execution_count": 10,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "anyBFlat.octaveIsImplicit"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "Set `.octave` yourself and `.octaveIsImplicit` becomes `False`."
+   ]
+  },
   {
    "cell_type": "markdown",
    "metadata": {},
@@ -233,7 +318,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 9,
+   "execution_count": 11,
    "metadata": {},
    "outputs": [
     {
@@ -242,7 +327,7 @@
        "'D#3'"
       ]
      },
-     "execution_count": 9,
+     "execution_count": 11,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -263,7 +348,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 10,
+   "execution_count": 12,
    "metadata": {},
    "outputs": [
     {
@@ -272,7 +357,7 @@
        "<music21.pitch.Pitch C##4>"
       ]
      },
-     "execution_count": 10,
+     "execution_count": 12,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -306,7 +391,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 11,
+   "execution_count": 13,
    "metadata": {},
    "outputs": [
     {
@@ -315,7 +400,7 @@
        "'C#'"
       ]
      },
-     "execution_count": 11,
+     "execution_count": 13,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -327,7 +412,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 12,
+   "execution_count": 14,
    "metadata": {},
    "outputs": [
     {
@@ -336,7 +421,7 @@
        "'C#'"
       ]
      },
-     "execution_count": 12,
+     "execution_count": 14,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -347,7 +432,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 13,
+   "execution_count": 15,
    "metadata": {},
    "outputs": [
     {
@@ -356,7 +441,7 @@
        "4"
       ]
      },
-     "execution_count": 13,
+     "execution_count": 15,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -367,7 +452,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 14,
+   "execution_count": 16,
    "metadata": {},
    "outputs": [
     {
@@ -376,7 +461,7 @@
        "4"
       ]
      },
-     "execution_count": 14,
+     "execution_count": 16,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -394,7 +479,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 15,
+   "execution_count": 17,
    "metadata": {},
    "outputs": [
     {
@@ -403,7 +488,7 @@
        "'do sostenido'"
       ]
      },
-     "execution_count": 15,
+     "execution_count": 17,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -421,7 +506,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 16,
+   "execution_count": 18,
    "metadata": {
     "tags": [
      "nbval-raises-exception"
@@ -453,7 +538,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 17,
+   "execution_count": 19,
    "metadata": {},
    "outputs": [
     {
@@ -477,7 +562,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 18,
+   "execution_count": 20,
    "metadata": {},
    "outputs": [
     {
@@ -550,7 +635,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 19,
+   "execution_count": 21,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -583,7 +668,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 20,
+   "execution_count": 22,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -604,7 +689,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 21,
+   "execution_count": 23,
    "metadata": {},
    "outputs": [
     {
@@ -613,7 +698,7 @@
        "1.5"
       ]
      },
-     "execution_count": 21,
+     "execution_count": 23,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -624,7 +709,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 22,
+   "execution_count": 24,
    "metadata": {},
    "outputs": [
     {
@@ -633,7 +718,7 @@
        "2.0"
       ]
      },
-     "execution_count": 22,
+     "execution_count": 24,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -652,7 +737,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 23,
+   "execution_count": 25,
    "metadata": {},
    "outputs": [
     {
@@ -661,7 +746,7 @@
        "'half'"
       ]
      },
-     "execution_count": 23,
+     "execution_count": 25,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -672,7 +757,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 24,
+   "execution_count": 26,
    "metadata": {},
    "outputs": [
     {
@@ -681,7 +766,7 @@
        "'quarter'"
       ]
      },
-     "execution_count": 24,
+     "execution_count": 26,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -703,7 +788,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 25,
+   "execution_count": 27,
    "metadata": {},
    "outputs": [
     {
@@ -712,7 +797,7 @@
        "0"
       ]
      },
-     "execution_count": 25,
+     "execution_count": 27,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -723,7 +808,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 26,
+   "execution_count": 28,
    "metadata": {},
    "outputs": [
     {
@@ -732,7 +817,7 @@
        "1"
       ]
      },
-     "execution_count": 26,
+     "execution_count": 28,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -754,7 +839,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 27,
+   "execution_count": 29,
    "metadata": {},
    "outputs": [
     {
@@ -763,7 +848,7 @@
        "1.75"
       ]
      },
-     "execution_count": 27,
+     "execution_count": 29,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -775,7 +860,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 28,
+   "execution_count": 30,
    "metadata": {},
    "outputs": [
     {
@@ -784,7 +869,7 @@
        "1.875"
       ]
      },
-     "execution_count": 28,
+     "execution_count": 30,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -796,7 +881,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 29,
+   "execution_count": 31,
    "metadata": {},
    "outputs": [
     {
@@ -805,7 +890,7 @@
        "1.9375"
       ]
      },
-     "execution_count": 29,
+     "execution_count": 31,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -825,7 +910,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 30,
+   "execution_count": 32,
    "metadata": {},
    "outputs": [
     {
@@ -834,7 +919,7 @@
        "'16th'"
       ]
      },
-     "execution_count": 30,
+     "execution_count": 32,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -846,7 +931,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 31,
+   "execution_count": 33,
    "metadata": {},
    "outputs": [
     {
@@ -855,7 +940,7 @@
        "0"
       ]
      },
-     "execution_count": 31,
+     "execution_count": 33,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -913,7 +998,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 47,
+   "execution_count": 34,
    "metadata": {},
    "outputs": [
     {
@@ -922,7 +1007,7 @@
        "<music21.pitch.Pitch C4>"
       ]
      },
-     "execution_count": 47,
+     "execution_count": 34,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -934,7 +1019,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 48,
+   "execution_count": 35,
    "metadata": {},
    "outputs": [
     {
@@ -943,7 +1028,7 @@
        "<music21.duration.Duration 1.0>"
       ]
      },
-     "execution_count": 48,
+     "execution_count": 35,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -961,7 +1046,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 49,
+   "execution_count": 36,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -978,7 +1063,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 50,
+   "execution_count": 37,
    "metadata": {},
    "outputs": [
     {
@@ -987,7 +1072,7 @@
        "'half'"
       ]
      },
-     "execution_count": 50,
+     "execution_count": 37,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -998,7 +1083,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 51,
+   "execution_count": 38,
    "metadata": {},
    "outputs": [
     {
@@ -1007,7 +1092,7 @@
        "1"
       ]
      },
-     "execution_count": 51,
+     "execution_count": 38,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -1018,7 +1103,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 52,
+   "execution_count": 39,
    "metadata": {},
    "outputs": [
     {
@@ -1027,7 +1112,7 @@
        "'E-'"
       ]
      },
-     "execution_count": 52,
+     "execution_count": 39,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -1038,7 +1123,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 53,
+   "execution_count": 40,
    "metadata": {},
    "outputs": [
     {
@@ -1047,7 +1132,7 @@
        "<music21.pitch.Accidental flat>"
       ]
      },
-     "execution_count": 53,
+     "execution_count": 40,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -1058,7 +1143,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 54,
+   "execution_count": 41,
    "metadata": {},
    "outputs": [
     {
@@ -1067,7 +1152,7 @@
        "5"
       ]
      },
-     "execution_count": 54,
+     "execution_count": 41,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -1087,7 +1172,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 55,
+   "execution_count": 42,
    "metadata": {},
    "outputs": [
     {
@@ -1096,7 +1181,7 @@
        "'E-'"
       ]
      },
-     "execution_count": 55,
+     "execution_count": 42,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -1107,7 +1192,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 56,
+   "execution_count": 43,
    "metadata": {},
    "outputs": [
     {
@@ -1116,7 +1201,7 @@
        "3.0"
       ]
      },
-     "execution_count": 56,
+     "execution_count": 43,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -1134,7 +1219,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 57,
+   "execution_count": 44,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -1153,7 +1238,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 58,
+   "execution_count": 45,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -1173,7 +1258,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 59,
+   "execution_count": 46,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -1191,7 +1276,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 60,
+   "execution_count": 47,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -1215,7 +1300,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 61,
+   "execution_count": 48,
    "metadata": {},
    "outputs": [
     {
@@ -1250,7 +1335,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 62,
+   "execution_count": 49,
    "metadata": {},
    "outputs": [
     {
diff --git a/music21/capella/fromCapellaXML.py b/music21/capella/fromCapellaXML.py
index 820cf6e967..8730568e7e 100644
--- a/music21/capella/fromCapellaXML.py
+++ b/music21/capella/fromCapellaXML.py
@@ -539,7 +539,7 @@ def noteFromHead(self, headElement: ET.Element) -> note.Note:
         noteNameWithOctave = headElement.attrib['pitch']
         n = note.Note()
         n.nameWithOctave = noteNameWithOctave
-        n.octave = n.pitch.implicitOctave - 1  # capella octaves are 1 off
+        n.octave = n.pitch.octave - 1  # capella octaves are 1 off
 
         alters = headElement.findall('alter')
         if len(alters) > 1:
diff --git a/music21/chord/__init__.py b/music21/chord/__init__.py
index 3c5a16330c..a0d6789f68 100644
--- a/music21/chord/__init__.py
+++ b/music21/chord/__init__.py
@@ -1544,9 +1544,6 @@ def closedPosition(
         pBass = returnObj.bass()  # returns a reference, not a copy
         if forceOctave is not None:
             pBassOctave = pBass.octave
-            if pBassOctave is None:
-                pBassOctave = pBass.implicitOctave
-
             if pBassOctave > forceOctave:
                 dif = -1
             elif pBassOctave < forceOctave:
@@ -1557,16 +1554,13 @@ def closedPosition(
                 while pBass.octave != forceOctave:
                     # shift octave of all pitches
                     for p in returnObj.pitches:
-                        if p.octave is None:
-                            p.octave = p.implicitOctave
                         p.octave += dif
 
         # can change these pitches in place
         for p in returnObj.pitches:
             # bring each pitch down octaves until pitch space is
             # within an octave
-            if p.octave is None:
-                p.octave = p.implicitOctave
+            p.octaveIsImplicit = False
             while p.ps >= pBass.ps + 12:
                 p.octave -= 1
             # check for a bass of C4 and the note B#7 added to it, should be B#4 not B#3...
@@ -2394,10 +2388,7 @@ def _setInversion(
             currentMaxMidi = max(self.pitches).ps
             tempBassPitch = self.bass()
             while tempBassPitch.ps < currentMaxMidi:
-                if tempBassPitch.octave is not None:
-                    tempBassPitch.octave += 1
-                else:
-                    tempBassPitch.octave = tempBassPitch.implicitOctave + 1
+                tempBassPitch.octave += 1
 
             # housekeeping for next loop tests
             self.clearCache()
@@ -4012,7 +4003,7 @@ def semiClosedPosition(
                 if p.step not in usedSteps:
                     usedSteps.append(p.step)
                 else:
-                    p.octave = p.implicitOctave + 1
+                    p.octave += 1
                     newRemainingPitches.append(p)
             remainingPitches = newRemainingPitches
 
diff --git a/music21/expressions.py b/music21/expressions.py
index fbecb96bf7..bcbf71a59d 100644
--- a/music21/expressions.py
+++ b/music21/expressions.py
@@ -760,8 +760,7 @@ def getSize(
 
         ornamentalPitch: pitch.Pitch = copy.deepcopy(srcPitch)
         ornamentalPitch.accidental = None
-        if ornamentalPitch.octave is None:
-            ornamentalPitch.octave = ornamentalPitch.implicitOctave
+        ornamentalPitch.octaveIsImplicit = False
 
         if self._direction == 'up':
             ornamentalPitch.transpose(interval.GenericInterval(2), inPlace=True)
@@ -828,8 +827,7 @@ def resolveOrnamentalPitches(
         transposeInterval: interval.IntervalBase = self.getSize(srcObj, keySig=keySig)
 
         ornamentalPitch: pitch.Pitch = copy.deepcopy(srcPitch)
-        if ornamentalPitch.octave is None:
-            ornamentalPitch.octave = ornamentalPitch.implicitOctave
+        ornamentalPitch.octaveIsImplicit = False
         ornamentalPitch.transpose(transposeInterval, inPlace=True)
         # if there are microtones, see if they can be converted to quarter tones.
         if ornamentalPitch.microtone.cents != 0:
@@ -1375,8 +1373,7 @@ def getSize(
 
         ornamentalPitch: pitch.Pitch = copy.deepcopy(srcPitch)
         ornamentalPitch.accidental = None
-        if ornamentalPitch.octave is None:
-            ornamentalPitch.octave = ornamentalPitch.implicitOctave
+        ornamentalPitch.octaveIsImplicit = False
 
         if self._direction == 'up':
             ornamentalPitch.transpose(interval.GenericInterval(2), inPlace=True)
@@ -1424,8 +1421,7 @@ def resolveOrnamentalPitches(
         transposeInterval: interval.IntervalBase = self.getSize(srcObj, keySig=keySig)
 
         ornamentalPitch: pitch.Pitch = copy.deepcopy(srcPitch)
-        if ornamentalPitch.octave is None:
-            ornamentalPitch.octave = ornamentalPitch.implicitOctave
+        ornamentalPitch.octaveIsImplicit = False
         ornamentalPitch.transpose(transposeInterval, inPlace=True)
         # if there are microtones, see if they can be converted to quarter tones.
         if ornamentalPitch.microtone.cents != 0:
@@ -2043,8 +2039,7 @@ def getSize(
 
         ornamentalPitch: pitch.Pitch = copy.deepcopy(srcPitch)
         ornamentalPitch.accidental = None
-        if ornamentalPitch.octave is None:
-            ornamentalPitch.octave = ornamentalPitch.implicitOctave
+        ornamentalPitch.octaveIsImplicit = False
 
         accidental: pitch.Accidental|None = None
         if which == 'upper':
@@ -2119,16 +2114,14 @@ def resolveOrnamentalPitches(
             srcObj, 'lower', keySig=keySig)
 
         upperPitch: pitch.Pitch = copy.deepcopy(srcPitch)
-        if upperPitch.octave is None:
-            upperPitch.octave = upperPitch.implicitOctave
+        upperPitch.octaveIsImplicit = False
         upperPitch.transpose(transposeIntervalUp, inPlace=True)
         # if there are microtones, see if they can be converted to quarter tones.
         if upperPitch.microtone.cents != 0:
             upperPitch.convertMicrotonesToQuarterTones(inPlace=True)
 
         lowerPitch: pitch.Pitch = copy.deepcopy(srcPitch)
-        if lowerPitch.octave is None:
-            lowerPitch.octave = lowerPitch.implicitOctave
+        lowerPitch.octaveIsImplicit = False
         lowerPitch.transpose(transposeIntervalDown, inPlace=True)
         # if there are microtones, see if they can be converted to quarter tones.
         if lowerPitch.microtone.cents != 0:
diff --git a/music21/figuredBass/realizerScale.py b/music21/figuredBass/realizerScale.py
index 3f3345fc19..a1b6575dcd 100644
--- a/music21/figuredBass/realizerScale.py
+++ b/music21/figuredBass/realizerScale.py
@@ -203,7 +203,7 @@ def getPitches(self,
         bassPitch = convertToPitch(bassPitch)
         maxPitch = convertToPitch(maxPitch)
         pitchNames = self.getPitchNames(bassPitch, notationString)
-        maxOctave = maxPitch.implicitOctave
+        maxOctave = maxPitch.octave
         iter1 = itertools.product(pitchNames, range(maxOctave + 1))
         iter2 = map(lambda x: pitch.Pitch(x[0] + str(x[1])), iter1)
         iter3 = itertools.filterfalse(lambda samplePitch: bassPitch > samplePitch, iter2)
diff --git a/music21/figuredBass/segment.py b/music21/figuredBass/segment.py
index 5bf60d4818..466ccca6d0 100644
--- a/music21/figuredBass/segment.py
+++ b/music21/figuredBass/segment.py
@@ -930,15 +930,15 @@ def getPitches(pitchNames: Iterable[str] = ('C', 'E', 'G'),
 
     >>> segment.getPitches(maxPitch=pitch.Pitch('E'))
     Traceback (most recent call last):
-    ValueError: maxPitch must be given an octave
+    ValueError: maxPitch must not have an implicit octave
     '''
     if isinstance(bassPitch, str):
         bassPitch = pitch.Pitch(bassPitch)
     if isinstance(maxPitch, str):
         maxPitch = pitch.Pitch(maxPitch)
 
-    if maxPitch.octave is None:
-        raise ValueError('maxPitch must be given an octave')
+    if maxPitch.octaveIsImplicit:
+        raise ValueError('maxPitch must not have an implicit octave')
     iter1 = itertools.product(pitchNames, range(maxPitch.octave + 1))
     iter2 = map(lambda x: pitch.Pitch(x[0] + str(x[1])), iter1)
     iter3 = itertools.filterfalse(lambda samplePitch: bassPitch > samplePitch, iter2)
diff --git a/music21/harmony.py b/music21/harmony.py
index f9d152f2c7..1210fc6ad8 100644
--- a/music21/harmony.py
+++ b/music21/harmony.py
@@ -2676,10 +2676,6 @@ def testHarmonyPreservesInversionAndBass(self):
         self.assertEqual(explicitFm6.root(find=False).name, 'F')
         fm6bassOctave = explicitFm6.bass(find=False).octave
         fm6rootOctave = explicitFm6.root(find=False).octave
-        self.assertIsNotNone(fm6bassOctave)
-        self.assertIsNotNone(fm6rootOctave)
-        assert fm6bassOctave is not None
-        assert fm6rootOctave is not None
         self.assertLess(fm6bassOctave, fm6rootOctave)
 
     def testClassSortOrderHarmony(self):
diff --git a/music21/interval.py b/music21/interval.py
index 2390cdaa1b..01cac6ca4f 100644
--- a/music21/interval.py
+++ b/music21/interval.py
@@ -1409,10 +1409,7 @@ def transposePitch(self, p: pitch.Pitch, *, inPlace=False):
         >>> gSharp
         <music21.pitch.Pitch D#5>
         '''
-        if p.octave is None:
-            useImplicitOctave = True
-        else:
-            useImplicitOctave = False
+        useImplicitOctave = p.octaveIsImplicit
         pitchDNN = p.diatonicNoteNum
 
         if inPlace:
@@ -1422,7 +1419,7 @@ def transposePitch(self, p: pitch.Pitch, *, inPlace=False):
 
         newPitch.diatonicNoteNum = pitchDNN + self.staffDistance
         if useImplicitOctave:
-            newPitch.octave = None
+            newPitch.octaveIsImplicit = True
 
         if not inPlace:
             return newPitch
@@ -2500,10 +2497,7 @@ def transposePitch(self, p: pitch.Pitch, *, inPlace=False):
 
         * Changed in v6: added inPlace.
         '''
-        if p.octave is None:
-            useImplicitOctave = True
-        else:
-            useImplicitOctave = False
+        useImplicitOctave = p.octaveIsImplicit
         pps = p.ps
 
         if not inPlace:
@@ -2512,8 +2506,8 @@ def transposePitch(self, p: pitch.Pitch, *, inPlace=False):
             newPitch = p
 
         newPitch.ps = pps + self.semitones
-        if useImplicitOctave is True:
-            newPitch.octave = None
+        if useImplicitOctave:
+            newPitch.octaveIsImplicit = True
 
         if not inPlace:
             return newPitch
@@ -3426,8 +3420,8 @@ def transposePitch(self,
                 maxAccidental=maxAccidental,
             )
 
-            if p.fundamental.octave is None:
-                pOut.fundamental.octave = None
+            if p.fundamental.octaveIsImplicit:
+                pOut.fundamental.octaveIsImplicit = True
 
         if not inPlace:
             return pOut
@@ -3450,10 +3444,7 @@ def _diatonicTransposePitch(self,
             # true unison and any multiple of true octave
             inheritAccidentalDisplayStatus = True
 
-        if p.octave is None:
-            useImplicitOctave = True
-        else:
-            useImplicitOctave = False
+        useImplicitOctave = p.octaveIsImplicit
 
         pitch1 = p
         pitch2 = copy.deepcopy(pitch1)
@@ -3543,7 +3534,7 @@ def _diatonicTransposePitch(self,
             pitch2.microtone = pitch2.microtone.cents + centsOrigin
 
         if useImplicitOctave:
-            pitch2.octave = None
+            pitch2.octaveIsImplicit = True
 
         if not inPlace:
             return pitch2
diff --git a/music21/key.py b/music21/key.py
index ffc80d7ca4..631a49a13c 100644
--- a/music21/key.py
+++ b/music21/key.py
@@ -127,7 +127,7 @@ def sharpsToPitch(sharpCount: int) -> pitch.Pitch:
         return copy.deepcopy(_sharpsToPitchCache[sharpCount])
 
     pitchInit = pitch.Pitch('C')
-    pitchInit.octave = None
+    pitchInit.octaveIsImplicit = True
     # keyPc = (self.sharps * 7) % 12
     if sharpCount > 0:
         intervalStr = 'P5'
@@ -139,7 +139,7 @@ def sharpsToPitch(sharpCount: int) -> pitch.Pitch:
     intervalObj = interval.Interval(intervalStr)
     for i in range(abs(sharpCount)):
         pitchInit = intervalObj.transposePitch(pitchInit)
-    pitchInit.octave = None
+    pitchInit.octaveIsImplicit = True
 
     _sharpsToPitchCache[sharpCount] = pitchInit
     return pitchInit
@@ -518,7 +518,7 @@ def alteredPitches(self) -> list[pitch.Pitch]:
             for i in range(self.sharps):
                 pKeep.transpose('P5', inPlace=True)
                 p = copy.deepcopy(pKeep)
-                p.octave = None
+                p.octaveIsImplicit = True
                 post.append(p)
 
         elif self.sharps < 0:
@@ -526,7 +526,7 @@ def alteredPitches(self) -> list[pitch.Pitch]:
             for i in range(abs(self.sharps)):
                 pKeep.transpose('P4', inPlace=True)
                 p = copy.deepcopy(pKeep)
-                p.octave = None
+                p.octaveIsImplicit = True
                 post.append(p)
 
         return post
@@ -780,7 +780,7 @@ def transposePitchFromC(self, p: pitch.Pitch, *, inPlace=False) -> pitch.Pitch|N
         for i in range(transTimes):
             transInterval.transposePitch(p, inPlace=True)
 
-        if originalOctave is not None:
+        if not p.octaveIsImplicit:
             p.octave = originalOctave
 
         if not inPlace:
diff --git a/music21/lily/translate.py b/music21/lily/translate.py
index c573246baa..335c9728e4 100644
--- a/music21/lily/translate.py
+++ b/music21/lily/translate.py
@@ -1514,12 +1514,12 @@ def octaveCharactersFromPitch(self, pitchObj: pitch.Pitch) -> str:
         returns a string of single-quotes or commas or '' representing
         the octave of a :class:`~music21.pitch.Pitch` object
         '''
-        implicitOctave = pitchObj.implicitOctave
-        if implicitOctave < 3:
-            correctedOctave = 3 - implicitOctave
+        octave = pitchObj.octave
+        if octave < 3:
+            correctedOctave = 3 - octave
             octaveModChars = ',' * correctedOctave  # C2 = c,  C1 = c,,
         else:
-            correctedOctave = implicitOctave - 3
+            correctedOctave = octave - 3
             octaveModChars = "'" * correctedOctave  # C4 = c', C5 = c''  etc.
         return octaveModChars
 
diff --git a/music21/musedata/base40.py b/music21/musedata/base40.py
index 073537e524..3a4d6c5417 100644
--- a/music21/musedata/base40.py
+++ b/music21/musedata/base40.py
@@ -233,7 +233,7 @@ def base40ToPitch(base40Num: int) -> pitch.Pitch:
     '''
     p = pitch.Pitch()
     p.octave = ((base40Num - 1) / 40) + 1
-    tableNum = base40Num - 40 * (p.implicitOctave - 1)
+    tableNum = base40Num - 40 * (p.octave - 1)
     pitchName = base40Equivalent.get(tableNum, '')
     if pitchName:
         p.name = pitchName
@@ -266,7 +266,7 @@ def pitchToBase40(pitchToConvert: str|pitch.Pitch) -> int:
         pitchObj = pitchToConvert
     if pitchObj.name in base40Representation:
         tableNum = base40Representation[pitchObj.name]
-        base40Num = (40 * (pitchObj.implicitOctave - 1)) + tableNum
+        base40Num = (40 * (pitchObj.octave - 1)) + tableNum
         return base40Num
 
     raise Base40Exception('Base40 cannot handle this pitch ' + pitchObj.nameWithOctave)
diff --git a/music21/musicxml/m21ToXml.py b/music21/musicxml/m21ToXml.py
index 605810d917..e54b522059 100644
--- a/music21/musicxml/m21ToXml.py
+++ b/music21/musicxml/m21ToXml.py
@@ -4580,7 +4580,7 @@ def pitchToXml(self, p: pitch.Pitch):
         if p.accidental is not None:
             mxAlter = SubElement(mxPitch, 'alter')
             mxAlter.text = str(common.numToIntOrFloat(p.accidental.alter))
-        _setTagTextFromAttribute(p, mxPitch, 'octave', 'implicitOctave')
+        _setTagTextFromAttribute(p, mxPitch, 'octave')
         return mxPitch
 
     def unpitchedToXml(self,
@@ -7397,7 +7397,7 @@ def keySignatureToXml(self, keyOrKeySignature: key.KeySignature) -> Element:
                 # TODO: key-accidental
 
         for i, p in enumerate(keyOrKeySignature.alteredPitches):
-            if p.octave is not None:
+            if not p.octaveIsImplicit:
                 mxKeyOctave = SubElement(mxKey, 'key-octave')
                 mxKeyOctave.text = str(p.octave)
                 mxKeyOctave.set('number', str(i + 1))
diff --git a/music21/note.py b/music21/note.py
index 9c0ff2a282..1d69923fce 100644
--- a/music21/note.py
+++ b/music21/note.py
@@ -5,7 +5,7 @@
 # Authors:      Michael Scott Asato Cuthbert
 #               Christopher Ariza
 #
-# Copyright:    Copyright © 2006-2024 Michael Scott Asato Cuthbert
+# Copyright:    Copyright © 2006-2026 Michael Scott Asato Cuthbert
 # License:      BSD, see license.txt
 # ------------------------------------------------------------------------------
 '''
@@ -1446,10 +1446,10 @@ class Note(NotRest):
     >>> n = note.Note('B-')
     >>> n.name
     'B-'
-    >>> n.octave is None
-    True
-    >>> n.pitch.implicitOctave
+    >>> n.octave
     4
+    >>> n.pitch.octaveIsImplicit
+    True
 
     >>> n = note.Note(name='D#')
     >>> n.name
@@ -1657,15 +1657,17 @@ def step(self, value: StepName):
         self.pitch.step = value
 
     @property
-    def octave(self) -> int|None:
+    def octave(self) -> int:
         '''
         Return or set the octave value from the :class:`~music21.pitch.Pitch` object.
         See :attr:`~music21.pitch.Pitch.octave`.
+
+        * Changed in v11: always an int; see :attr:`~music21.pitch.Pitch.octaveIsImplicit`.
         '''
         return self.pitch.octave
 
     @octave.setter
-    def octave(self, value: int|None):
+    def octave(self, value: int|float|None):
         self.pitch.octave = value
 
     @property
@@ -1886,7 +1888,7 @@ def __init__(
         if displayName:
             display_pitch = Pitch(displayName)
             self.displayStep = display_pitch.step
-            self.displayOctave = display_pitch.implicitOctave
+            self.displayOctave = display_pitch.octave
 
     def _reprInternal(self):
         if not self.storedInstrument:
diff --git a/music21/pitch.py b/music21/pitch.py
index feb281a4da..dba07baa3e 100644
--- a/music21/pitch.py
+++ b/music21/pitch.py
@@ -5,7 +5,7 @@
 # Authors:      Michael Scott Asato Cuthbert
 #               Christopher Ariza
 #
-# Copyright:    Copyright © 2008-2019 Michael Scott Asato Cuthbert
+# Copyright:    Copyright © 2008-2026 Michael Scott Asato Cuthbert
 # License:      BSD, see license.txt
 # ------------------------------------------------------------------------------
 '''
@@ -579,7 +579,7 @@ def _dissonanceScore(pitches: list[Pitch],
             intervals = []
             for p1, p2 in itertools.combinations(pitches, 2):
                 p2 = copy.deepcopy(p2)
-                p2.octave = None
+                p2.octaveIsImplicit = True
                 this_interval = interval.Interval(noteStart=p1, noteEnd=p2)
                 intervals.append(this_interval)
         except interval.IntervalException:
@@ -1681,31 +1681,29 @@ class Pitch(prebase.ProtoM21Object):
         >>> alters
         [1.0, -1.0]
 
-    If a `Pitch` doesn't have an associated octave, then its
-    `.octave` value is None.  This means that it represents
-    any G#, regardless of octave.  Transposing this note up
-    an octave doesn't change anything.
+    A `Pitch` created without an octave represents any G#, regardless
+    of octave: it prints without an octave number, and transposing it
+    up an octave changes nothing.
 
     >>> anyGSharp = pitch.Pitch('G#')
-    >>> anyGSharp.octave is None
-    True
+    >>> anyGSharp
+    <music21.pitch.Pitch G#>
     >>> print(anyGSharp.transpose('P8'))
     G#
 
-    Sometimes we need an octave for a `Pitch` even if it's not
-    specified.  For instance, we can't play an octave-less `Pitch`
-    in MIDI or display it on a staff.  So there is an `.implicitOctave`
-    tag to deal with these situations; by default it's always 4 (unless
-    defaults.pitchOctave is changed)
+    Yet an octave is often needed anyhow, to play the `Pitch` in MIDI or
+    put it on a staff, so `.octave` is always an integer: the default octave,
+    4 (`defaults.pitchOctave`), when none was given.  `.octaveIsImplicit`
+    tells the two cases apart.
 
-    >>> anyGSharp.implicitOctave
+    >>> anyGSharp.octave
     4
-
-    If a `Pitch` has its `.octave` explicitly set, then `.implicitOctave`
-    always equals `.octave`.
-
-    >>> highEflat.implicitOctave
+    >>> anyGSharp.octaveIsImplicit
+    True
+    >>> highEflat.octave
     6
+    >>> highEflat.octaveIsImplicit
+    False
 
     If an integer or float >= 12 is passed to the constructor then it is
     used as the `.ps` attribute, which is for most common piano notes, the
@@ -1724,7 +1722,7 @@ class Pitch(prebase.ProtoM21Object):
     >>> p2 = pitch.Pitch(3)
     >>> p2
     <music21.pitch.Pitch E->
-    >>> p2.octave is None
+    >>> p2.octaveIsImplicit
     True
 
     Since in instantiating pitches from numbers,
@@ -1846,8 +1844,8 @@ class Pitch(prebase.ProtoM21Object):
     and cannot be put into Streams
     '''
     # define order for presenting names in documentation; use strings
-    _DOC_ORDER = ['name', 'nameWithOctave', 'step', 'pitchClass', 'octave', 'midi', 'german',
-                  'french', 'spanish', 'italian', 'dutch']
+    _DOC_ORDER = ['name', 'nameWithOctave', 'step', 'pitchClass', 'octave', 'octaveIsImplicit',
+                  'midi', 'german', 'french', 'spanish', 'italian', 'dutch']
     # documentation for all attributes (not properties or methods)
     # _DOC_ATTR: dict[str, str] = {
     # }
@@ -1934,12 +1932,7 @@ def __init__(self,
         # 5% of pitch creation time; it'll be created in a sec anyhow
         self._microtone: Microtone|None = None
 
-        # # CA, Q: should this remain an attribute or only refer to value in defaults?
-        # # MSC A: no, it's a useful attribute for cases such as scales where if there are
-        # #        no octaves we give a defaultOctave higher than the previous
-        # #        MSC 12 years later: maybe Chris was right!
-        # self.defaultOctave: int = defaults.pitchOctave
-        # # MSC: even later: Chris Ariza was right
+        # None means implicit: .octave then reports defaults.pitchOctave
         self._octave: int|None = None
 
         # if True, accidental is not known; is determined algorithmically
@@ -2046,7 +2039,7 @@ def __eq__(self, other: object) -> bool:
         '''
         if not isinstance(other, Pitch):
             return NotImplemented
-        if (self.octave == other.octave
+        if (self._octave == other._octave
                 and self.step == other.step
                 and self.accidental == other.accidental
                 and self.microtone == other.microtone):
@@ -2085,7 +2078,7 @@ def __hash__(self) -> int:
             self.fundamental,
             self.spellingIsInferred,
             self.microtone,
-            self.octave,
+            self._octave,
             self.step,
             type(self),
         )
@@ -2592,15 +2585,15 @@ def ps(self) -> float:
         >>> print(f'{p.ps:.1f}')
         60.2
 
-        Octaveless pitches use their .implicitOctave attributes:
+        A pitch without an octave of its own uses the default octave, 4:
 
         >>> d = pitch.Pitch('D#')
-        >>> d.octave is None
+        >>> d.octaveIsImplicit
         True
-        >>> d.implicitOctave
-        4
         >>> d.ps
         63.0
+        >>> d.ps == pitch.Pitch('D#4').ps
+        True
 
         >>> d.octave = 5
         >>> d.ps
@@ -2628,7 +2621,7 @@ def ps(self) -> float:
         or self.accidental are changed.
         '''
         step = self._step
-        ps = float(((self.implicitOctave + 1) * 12) + STEPREF[step])
+        ps = float(((self.octave + 1) * 12) + STEPREF[step])
         if self.accidental is not None:
             ps = ps + self.accidental.alter
         if self._microtone is not None:
@@ -2892,9 +2885,9 @@ def nameWithOctave(self) -> str:
         Traceback (most recent call last):
         music21.pitch.PitchException: Cannot set a nameWithOctave with 'C#'
 
-        Set octave to None explicitly instead.
+        Set `.octaveIsImplicit = True` instead.
         '''
-        if self.octave is None:
+        if self.octaveIsImplicit:
             return self.name
         else:
             return self.name + str(self.octave)
@@ -2922,7 +2915,7 @@ def unicodeNameWithOctave(self) -> str:
         >>> p.unicodeNameWithOctave
         'C♯4'
         '''
-        if self.octave is None:
+        if self.octaveIsImplicit:
             return self.unicodeName
         else:
             return self.unicodeName + str(self.octave)
@@ -2948,7 +2941,7 @@ def fullName(self) -> str:
         if self.accidental is not None:
             name += f'-{self.accidental.fullName}'
 
-        if self.octave is not None:
+        if not self.octaveIsImplicit:
             name += f' in octave {self.octave}'
 
         if self._microtone is not None and self.microtone.cents != 0:
@@ -3166,31 +3159,42 @@ def pitchClassString(self, v: int|PitchClassString) -> None:
 
 
     @property
-    def octave(self) -> int|None:
+    def octave(self) -> int:
         '''
-        Returns or sets the octave of the note.
-        Setting the octave updates the pitchSpace attribute.
+        Returns or sets the octave of the Pitch.
 
-        >>> a = pitch.Pitch('g')
-        >>> a.octave is None
-        True
-        >>> a.implicitOctave
+        >>> b = pitch.Pitch('B5')
+        >>> b.octave
+        5
+
+        Always an int: a Pitch created without an octave reports the default
+        octave, 4 (`defaults.pitchOctave`), and has `.octaveIsImplicit` True.
+
+        >>> g = pitch.Pitch('g')
+        >>> g.octave
         4
-        >>> a.ps  ## will use implicitOctave
+        >>> g.octaveIsImplicit
+        True
+        >>> g.ps
         67.0
-        >>> a.name
-        'G'
 
-        >>> a.octave = 14
-        >>> a.octave
-        14
-        >>> a.implicitOctave
+        Setting the octave updates `.ps` and makes the octave explicit:
+
+        >>> g.octave = 14
+        >>> g.octave
         14
-        >>> a.name
-        'G'
-        >>> a.ps
+        >>> g.octaveIsImplicit
+        False
+        >>> g.ps
         187.0
+
+        To make the pitch octaveless, set `.octaveIsImplicit = True`.  Setting
+        `.octave = None` is deprecated and will be removed in v13.
+
+        * Changed in v11: always an int; `.octaveIsImplicit` says whether it was given.
         '''
+        if self._octave is None:
+            return defaults.pitchOctave
         return self._octave
 
     @octave.setter
@@ -3198,28 +3202,64 @@ def octave(self, value: int|float|None) -> None:
         if value is not None:
             self._octave = int(value)
         else:
+            # None is deprecated, removed in v13. Add real deprecation message here in v12
             self._octave = None
         self.informClient()
 
+    @property
+    def octaveIsImplicit(self) -> bool:
+        '''
+        True if this Pitch was never given an octave, so it stands for its
+        pitch class in any octave: it prints without an octave number, and
+        `.octave` reports the default, 4.
+
+        >>> anyFSharp = pitch.Pitch('F#')
+        >>> anyFSharp.octaveIsImplicit
+        True
+        >>> anyFSharp
+        <music21.pitch.Pitch F#>
+        >>> anyFSharp.octave
+        4
+
+        Setting `.octave` makes the octave explicit:
+
+        >>> anyFSharp.octave = 5
+        >>> anyFSharp.octaveIsImplicit
+        False
+        >>> anyFSharp
+        <music21.pitch.Pitch F#5>
+
+        Set it back to True to make the pitch octaveless again:
+
+        >>> anyFSharp.octaveIsImplicit = True
+        >>> anyFSharp
+        <music21.pitch.Pitch F#>
+
+        * New in v11.
+        '''
+        return self._octave is None
+
+    @octaveIsImplicit.setter
+    def octaveIsImplicit(self, value: bool) -> None:
+        if bool(value) == self.octaveIsImplicit:
+            return
+        self._octave = None if value else defaults.pitchOctave
+        self.informClient()
+
     @property
     def implicitOctave(self) -> int:
         '''
-        Returns the octave of the Pitch, or defaultOctave if
-        octave was never set. To set an octave, use .octave.
-        Default octave is usually 4.
+        Synonym for `.octave`.
 
         >>> p = pitch.Pitch('C#')
-        >>> p.octave is None
-        True
         >>> p.implicitOctave
         4
 
-        Cannot be set.  Instead, just change the `.octave` of the pitch
+        * Deprecated in v11: use `.octave`, which is now always an int.
+          A warning arrives in v12 and the property goes away later.
         '''
-        if self.octave is None:
-            return defaults.pitchOctave
-        else:
-            return self.octave
+        # Add real deprecation message here in v12
+        return self.octave
 
     # noinspection SpellCheckingInspection,GrazieInspection
     @property
@@ -4006,7 +4046,7 @@ def isEnharmonic(self, other: Pitch) -> bool:
         >>> pD4.isEnharmonic(pEbb4) and pD4.step == pEbb4.step
         False
         '''
-        if other.octave is None or self.octave is None:
+        if other.octaveIsImplicit or self.octaveIsImplicit:
             return (other.ps - self.ps) % 12 == 0
         else:
             # if pitch spaces are equal, these are enharmonics
@@ -4040,19 +4080,19 @@ def _getEnharmonicHelper(self,
         if intervalString not in self._transpositionIntervals:
             self._transpositionIntervals[intervalString] = interval.Interval(intervalString)
         intervalObj = self._transpositionIntervals[intervalString]
-        octaveStored = self.octave  # may be None
+        octaveWasImplicit = self.octaveIsImplicit
         p = intervalObj.transposePitch(self, maxAccidental=None)
         if not inPlace:
-            if octaveStored is None:
-                p.octave = None
+            if octaveWasImplicit:
+                p.octaveIsImplicit = True
             return p
         else:
             self.step = p.step
             self.accidental = p.accidental
             if p.microtone is not None:
                 self.microtone = p.microtone
-            if octaveStored is None:
-                self.octave = None
+            if octaveWasImplicit:
+                self.octaveIsImplicit = True
             else:
                 self.octave = p.octave
             return None
@@ -4231,10 +4271,10 @@ def simplifyEnharmonic(
             else:
                 # by resetting the pitch space value, we will get a simpler
                 # enharmonic spelling
-                saveOctave = self.octave
+                octaveWasImplicit = self.octaveIsImplicit
                 returnObj.ps = self.ps
-                if saveOctave is None:
-                    returnObj.octave = None
+                if octaveWasImplicit:
+                    returnObj.octaveIsImplicit = True
 
         if mostCommon:
             if returnObj.name == 'D#':
@@ -4466,7 +4506,7 @@ def diatonicNoteNum(self) -> int:
         >>> b.diatonicNoteNum
         0
 
-        An `implicitOctave` of 4 is used if octave is not set:
+        The default octave, 4, is used as a basis if the pitch had no octave:
 
         >>> c = pitch.Pitch('C')
         >>> c.diatonicNoteNum
@@ -4496,7 +4536,7 @@ def diatonicNoteNum(self) -> int:
         >>> lowLowLowD.diatonicNoteNum
         -19
         '''
-        return STEP_TO_DNN_OFFSET[self.step] + 1 + (7 * self.implicitOctave)
+        return STEP_TO_DNN_OFFSET[self.step] + 1 + (7 * self.octave)
 
     @diatonicNoteNum.setter
     def diatonicNoteNum(self, newNum: int) -> None:
@@ -4641,7 +4681,7 @@ def transpose(
             # pitch attributes
             # NOTE: in some cases this may not return exactly the proper config
             self.name = p.name
-            if self.octave is not None:
+            if not self.octaveIsImplicit:
                 self.octave = p.octave
             # manually copy accidental object
             self.accidental = p.accidental
@@ -4725,14 +4765,13 @@ def transposeBelowTarget(
 
         * Changed in v3: default for inPlace=False.
         '''
-        if self.octave is None:
+        if self.octaveIsImplicit:
             raise PitchException('Cannot call transposeBelowTarget with an octaveless Pitch.')
 
         if inPlace:
             src = self
         else:
             src = copy.deepcopy(self)
-        assert src.octave is not None
 
         while True:
             # ref 20, min 10, lower ref.
@@ -4810,14 +4849,13 @@ def transposeAboveTarget(self,
 
         * Changed in v3: default for inPlace=False.
         '''
-        if self.octave is None:
+        if self.octaveIsImplicit:
             raise PitchException('Cannot call transposeAboveTarget with an octaveless Pitch.')
 
         if inPlace:
             src = self
         else:
             src = copy.deepcopy(self)
-        assert src.octave is not None
 
         # case where self is below target
         while True:
diff --git a/music21/roman.py b/music21/roman.py
index 52d5df146e..d9de8dc1f4 100644
--- a/music21/roman.py
+++ b/music21/roman.py
@@ -21,7 +21,6 @@
 
 from music21 import chord
 from music21 import common
-from music21 import defaults
 from music21 import environment
 from music21 import exceptions21
 from music21.figuredBass import notation as fbNotation
@@ -3416,12 +3415,9 @@ def _updatePitches(self) -> None:
                 thisScaleDegree, direction=scale.Direction.ASCENDING))
             pitchName = self.figuresNotationObj.modifiers[i].modifyPitchName(newPitch.name)
             newNewPitch = pitch.Pitch(pitchName)
-            if newPitch.octave is not None:
-                newNewPitch.octave = newPitch.octave
-            else:
-                newNewPitch.octave = defaults.pitchOctave
+            newNewPitch.octave = newPitch.octave
             if newNewPitch.ps < lastPitch.ps:
-                newNewPitch.octave += 1  # type: ignore
+                newNewPitch.octave += 1
             pitches.append(newNewPitch)
             lastPitch = newNewPitch
 
@@ -3480,13 +3476,13 @@ def _updatePitches(self) -> None:
                     addedPitch.accidental = pitch.Accidental(alteration)
 
                 while addedPitch.ps < bassPitch.ps:
-                    addedPitch.octave = addedPitch.implicitOctave + 1
+                    addedPitch.octave += 1
 
                 if (addedPitch.ps == bassPitch.ps
                         and addedPitch.diatonicNoteNum < bassPitch.diatonicNoteNum):
                     # RN('IV[add#7]', 'C') would otherwise result
                     # in E#4 as bass, not E#5 as highest note.
-                    addedPitch.octave = addedPitch.implicitOctave + 1
+                    addedPitch.octave += 1
 
                 if addedPitch not in self.pitches:
                     self.add(addedPitch)
diff --git a/music21/scale/__init__.py b/music21/scale/__init__.py
index 20ead29ffa..b48563c639 100644
--- a/music21/scale/__init__.py
+++ b/music21/scale/__init__.py
@@ -98,7 +98,6 @@
 # -------------------------
 from music21 import base
 from music21 import common
-from music21 import defaults
 from music21 import environment
 from music21 import exceptions21
 from music21 import note
@@ -250,8 +249,7 @@ def extractPitchList(
                 seen.add(hashValue)
                 post.append(p)
         for p in post:
-            if p.octave is None:
-                p.octave = defaults.pitchOctave
+            p.octaveIsImplicit = False
 
         return post
 
@@ -388,8 +386,7 @@ def buildNetworkFromPitches(
                 self.octaveDuplicating = False
         else:
             p = copy.deepcopy(pitchListProcessed[0])
-            if p.octave is None:
-                p.octave = p.implicitOctave
+            p.octaveIsImplicit = False
             if pitchListProcessed[-1] > pitchListProcessed[0]:  # ascending
                 while p.ps < pitchListProcessed[-1].ps:
                     p.octave += 1
@@ -426,10 +423,10 @@ def fixDefaultOctaveForPitchList(pitchList: list[pitch.Pitch]) -> list[pitch.Pit
         >>> pitchListStrs = 'a b c d e f g a'.split()
         >>> pitchList = [pitch.Pitch(p) for p in pitchListStrs]
 
-        Here's the problem, between `pitchList[1]` and `pitchList[2]` the `.implicitOctave`
-        stays the same, so the `.ps` drops:
+        Here's the problem, between `pitchList[1]` and `pitchList[2]` the `.octave`
+        stays the same (since both pitches have .octaveIsImplicit == True), so the `.ps` drops:
 
-        >>> (pitchList[1].implicitOctave, pitchList[2].implicitOctave)
+        >>> (pitchList[1].octave, pitchList[2].octave)
         (4, 4)
         >>> (pitchList[1].ps, pitchList[2].ps)
         (71.0, 60.0)
@@ -438,7 +435,7 @@ def fixDefaultOctaveForPitchList(pitchList: list[pitch.Pitch]) -> list[pitch.Pit
         one has a .ps above the previous:
 
         >>> pl2 = scale.AbstractScale.fixDefaultOctaveForPitchList(pitchList)
-        >>> (pl2[1].implicitOctave, pl2[2].implicitOctave, pl2[3].implicitOctave)
+        >>> (pl2[1].octave, pl2[2].octave, pl2[3].octave)
         (4, 5, 5)
         >>> (pl2[1].ps, pl2[2].ps)
         (71.0, 72.0)
@@ -452,9 +449,9 @@ def fixDefaultOctaveForPitchList(pitchList: list[pitch.Pitch]) -> list[pitch.Pit
         '''
         # fix defaultOctave for pitchList
         lastPs: float = 0
-        lastOctave = pitchList[0].implicitOctave
+        lastOctave = pitchList[0].octave
         for p in pitchList:
-            if p.octave is None:
+            if p.octaveIsImplicit:
                 if lastPs > p.ps:
                     p.octave = lastOctave
                 while lastPs > p.ps:
@@ -462,7 +459,7 @@ def fixDefaultOctaveForPitchList(pitchList: list[pitch.Pitch]) -> list[pitch.Pit
                     p.octave = lastOctave
 
             lastPs = p.ps
-            lastOctave = p.implicitOctave
+            lastOctave = p.octave
 
         return pitchList
 
diff --git a/music21/scale/intervalNetwork.py b/music21/scale/intervalNetwork.py
index 384b181a55..4b7e5eaecc 100644
--- a/music21/scale/intervalNetwork.py
+++ b/music21/scale/intervalNetwork.py
@@ -1370,13 +1370,14 @@ def nextPitch(
         if alteredDegrees and degree in alteredDegrees:
             alterSemitones = alteredDegrees[degree]['interval'].semitones
         alterSemitonesInt = t.cast('int', alterSemitones)
-        if ((usedNeighbor and getNeighbor == Direction.DESCENDING)
-                or (not usedNeighbor and direction == Direction.ASCENDING)):
-            while p.octave is not None and p.transpose(alterSemitonesInt) > pitchOriginObj:
-                p.octave -= 1
-        else:
-            while p.octave is not None and p.transpose(alterSemitonesInt) < pitchOriginObj:
-                p.octave += 1
+        if not p.octaveIsImplicit:
+            if ((usedNeighbor and getNeighbor == Direction.DESCENDING)
+                    or (not usedNeighbor and direction == Direction.ASCENDING)):
+                while p.transpose(alterSemitonesInt) > pitchOriginObj:
+                    p.octave -= 1
+            else:
+                while p.transpose(alterSemitonesInt) < pitchOriginObj:
+                    p.octave += 1
 
         # pitchObj = p
         n = self.nodes[foundNodeId]
@@ -1487,8 +1488,7 @@ def realizeAscending(
             nodeObj = t.cast(list[Node], self.nodeNameToNodes(nodeId))[0]
 
         # must set an octave for pitch reference, even if not given
-        if pitchReference.octave is None:
-            pitchReference.octave = pitchReference.implicitOctave
+        pitchReference.octaveIsImplicit = False
 
         if isinstance(minPitch, str):
             minPitch = pitch.Pitch(minPitch)
@@ -1675,8 +1675,7 @@ def realizeDescending(
             pitchRef = copy.deepcopy(pitchReference)
 
         # must set an octave for pitch reference, even if not given
-        if pitchRef.octave is None:
-            pitchRef.octave = 4
+        pitchRef.octaveIsImplicit = False
 
         # get first node if no node is provided
         if isinstance(nodeId, Node):
@@ -1861,8 +1860,7 @@ def realize(self,
             pitchRef = copy.deepcopy(pitchReference)
 
         # must set an octave for pitch reference, even if not given
-        if pitchRef.octave is None:
-            pitchRef.octave = pitchRef.implicitOctave
+        pitchRef.octaveIsImplicit = False
 
         minPitchObj: pitch.Pitch|None
         if isinstance(minPitch, str):
@@ -2383,9 +2381,8 @@ def getRelativeNodeId(
         else:
             pitchTargetObj = pitchTarget
 
-        saveOctave = pitchTargetObj.octave
-        if saveOctave is None:
-            pitchTargetObj.octave = pitchTargetObj.implicitOctave
+        octaveWasImplicit = pitchTargetObj.octaveIsImplicit
+        pitchTargetObj.octaveIsImplicit = False
 
         # try an octave spread first
         # if a scale degree is larger than an octave this will fail
@@ -2413,8 +2410,8 @@ def getRelativeNodeId(
                 if realizedNode not in post:  # may be more than one match
                     post.append(realizedNode)
 
-        if saveOctave is None:
-            pitchTargetObj.octave = None
+        if octaveWasImplicit:
+            pitchTargetObj.octaveIsImplicit = True
 
         if not post:
             return None
@@ -2459,10 +2456,9 @@ def getNeighborNodeIds(
         else:
             pitchTargetObj = pitchTarget
 
-        savedOctave = pitchTargetObj.octave
-        if savedOctave is None:
-            # don't alter permanently, in case a Pitch object was passed in.
-            pitchTargetObj.octave = pitchTargetObj.implicitOctave
+        # don't alter permanently, in case a Pitch object was passed in.
+        octaveWasImplicit = pitchTargetObj.octaveIsImplicit
+        pitchTargetObj.octaveIsImplicit = False
         # try an octave spread first
         # if a scale degree is larger than an octave this will fail
         minPitch = pitchTargetObj.transpose(-12, inPlace=False)
@@ -2484,8 +2480,8 @@ def getNeighborNodeIds(
                 return lowNeighbor, highNeighbor
             lowNeighbor = realizedNode
 
-        if savedOctave is None:
-            pitchTargetObj.octave = savedOctave
+        if octaveWasImplicit:
+            pitchTargetObj.octaveIsImplicit = True
         return None
 
     def getRelativeNodeDegree(
diff --git a/music21/serial.py b/music21/serial.py
index b98c6f7da4..c081368943 100644
--- a/music21/serial.py
+++ b/music21/serial.py
@@ -304,7 +304,7 @@ def __init__(self, row=None, **keywords):
             else:
                 n = pc
 
-            n.pitch.octave = None
+            n.pitch.octaveIsImplicit = True
             self.append(n)
 
     def _reprInternal(self):
@@ -399,7 +399,7 @@ def makeTwelveToneRow(self):
             n = note.Note()
             n.duration.quarterLength = 0.0
             n.pitch.pitchClass = thisPc
-            n.pitch.octave = None
+            n.pitch.octaveIsImplicit = True
             a.append(n)
         return a
 
@@ -700,7 +700,7 @@ def matrix(self):
                 n = note.Note()
                 n.duration.quarterLength = 0.0
                 n.pitch.pitchClass = p
-                n.pitch.octave = None
+                n.pitch.octaveIsImplicit = True
                 rowObject.append(n)
             matrixObj.insert(0, rowObject)
 
@@ -1286,7 +1286,7 @@ def pcToToneRow(pcSet):
     for thisPc in pcSet:
         n = note.Note()
         n.pitch.pitchClass = thisPc
-        n.pitch.octave = None
+        n.pitch.octaveIsImplicit = True
         a.append(n)
     return a
 
diff --git a/music21/stream/tests.py b/music21/stream/tests.py
index 6e49f36179..ef92fb2ff3 100644
--- a/music21/stream/tests.py
+++ b/music21/stream/tests.py
@@ -2909,9 +2909,9 @@ def testMakeAccidentalsOnChord(self):
 
         # Repeat the test without octaves and reset state
         low, high = augmented_octave.pitches
-        low.octave = None
+        low.octaveIsImplicit = True
         low.accidental = None
-        high.octave = None
+        high.octaveIsImplicit = True
         high.accidental.displayStatus = None
 
         s2.makeAccidentals(inPlace=True)
diff --git a/music21/test/test_pitch.py b/music21/test/test_pitch.py
index fbd4379bb8..3716d8e5b5 100644
--- a/music21/test/test_pitch.py
+++ b/music21/test/test_pitch.py
@@ -5,7 +5,7 @@
 # Authors:      Michael Scott Asato Cuthbert
 #               Christopher Ariza
 #
-# Copyright:    Copyright © 2008-2024 Michael Scott Asato Cuthbert
+# Copyright:    Copyright © 2008-2026 Michael Scott Asato Cuthbert
 # License:      BSD, see license.txt
 # ------------------------------------------------------------------------------
 from __future__ import annotations
@@ -16,6 +16,7 @@
 from music21 import common
 from music21 import converter
 from music21 import corpus
+from music21 import defaults
 from music21 import key
 from music21 import note
 from music21 import pitch
@@ -41,6 +42,79 @@ def testOctave(self):
         b = Pitch('B#3')
         self.assertEqual(b.octave, 3)
 
+    def testOctaveIsImplicit(self):
+        anyFSharp = Pitch('F#')
+        self.assertTrue(anyFSharp.octaveIsImplicit)
+        self.assertEqual(anyFSharp.octave, 4)
+        self.assertEqual(anyFSharp.implicitOctave, 4)
+        self.assertEqual(anyFSharp.nameWithOctave, 'F#')
+        self.assertEqual(anyFSharp.ps, 66.0)
+
+        anyFSharp.octave = 5
+        self.assertFalse(anyFSharp.octaveIsImplicit)
+        self.assertEqual(anyFSharp.octave, 5)
+        self.assertEqual(anyFSharp.implicitOctave, 5)
+        self.assertEqual(anyFSharp.nameWithOctave, 'F#5')
+
+        anyFSharp.octaveIsImplicit = True
+        self.assertEqual(anyFSharp.octave, 4)
+        self.assertEqual(anyFSharp.nameWithOctave, 'F#')
+        self.assertEqual(anyFSharp.ps, 66.0)
+
+        # False gives the default octave explicitly
+        anyFSharp.octaveIsImplicit = False
+        self.assertEqual(anyFSharp.nameWithOctave, 'F#4')
+
+        # octave = None still forgets the octave
+        anyFSharp.octave = None
+        self.assertTrue(anyFSharp.octaveIsImplicit)
+        self.assertEqual(anyFSharp.octave, 4)
+
+        # Notes proxy the int
+        self.assertEqual(note.Note('B-').octave, 4)
+        self.assertEqual(note.Note('B-3').octave, 3)
+
+        # the default is read live from defaults.pitchOctave
+        savedDefaultOctave = defaults.pitchOctave
+        try:
+            defaults.pitchOctave = 3
+            self.assertEqual(Pitch('C').octave, 3)
+            self.assertEqual(Pitch('C').ps, 48.0)
+            self.assertEqual(Pitch('C5').octave, 5)
+        finally:
+            defaults.pitchOctave = savedDefaultOctave
+
+        # creation paths
+        self.assertTrue(Pitch().octaveIsImplicit)
+        self.assertTrue(Pitch(3).octaveIsImplicit)  # pitch class
+        self.assertFalse(Pitch(65).octaveIsImplicit)  # midi
+        self.assertFalse(Pitch('C4').octaveIsImplicit)
+        self.assertFalse(Pitch('C', octave=4).octaveIsImplicit)
+        self.assertTrue(Pitch(step='D', accidental='#').octaveIsImplicit)
+        self.assertTrue(note.Note('B-').pitch.octaveIsImplicit)
+        self.assertFalse(note.Note().pitch.octaveIsImplicit)
+
+        # implicitness survives copying and transposition
+        anyD = Pitch('D')
+        self.assertTrue(copy.deepcopy(anyD).octaveIsImplicit)
+        self.assertTrue(anyD.transpose('M2').octaveIsImplicit)
+        self.assertTrue(anyD.transpose(3).octaveIsImplicit)
+        self.assertTrue(anyD.getEnharmonic().octaveIsImplicit)
+        self.assertFalse(Pitch('D4').transpose('M2').octaveIsImplicit)
+
+        # an implicit octave is not the same as an explicit default octave
+        self.assertNotEqual(Pitch('C'), Pitch('C4'))
+        self.assertEqual(Pitch('C'), Pitch('C'))
+        self.assertNotEqual(hash(Pitch('C')), hash(Pitch('C4')))
+
+        # the setter informs a Note client only when something changed
+        n = note.Note('C4')
+        n._cache['junk'] = 1
+        n.pitch.octaveIsImplicit = False
+        self.assertEqual(n._cache, {'junk': 1})
+        n.pitch.octaveIsImplicit = True
+        self.assertEqual(n._cache, {})
+
     def testNameSetting(self):
         with self.assertRaisesRegex(ValueError,
                                     r"Cannot have octave given before pitch name in '8D-4'\."):