Simple303

A simple, hands-on, and accessible virtual TB-303 bassline synthesizer using Open-303 with analogue-style 64-step sequencer.

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📖 About the Project

Simple303 was created as part of the "Simple" series of virtual instruments (alongside Simple606).

Modern Digital Audio Workstations (DAWs) and software synthesizers are often overloaded with complex routing matrices, deep menus, and steep learning curves. This project was born out of a desire to make electronic music-making immediately accessible, tactile, and fun for anyone—especially for people like my partner, for whom a traditional DAW is simply too overwhelming.

Simple303 focuses on immediate creative flow: turn knobs, punch in steps, hit random, chain patterns together, and make acid basslines without getting bogged down by software complexity.

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✨ Features

🎛️ Synthesizer Engine & Devil Fish Mods

• Dynamic Waveform Morphing: Smooth rotary morph between pure Sawtooth (0%) and Square (100%) waveforms.
• Classic TB-303 Filter Section: Dedicated controls for Tuning, Cutoff, Resonance, Envelope Modulation, Decay, and Accent.
• Analogue Drive: Built-in diode-clipping saturation for subtle warmth to gritty acid crunch.
• Devil Fish Modifications:
  • TRACKING: Variable keyboard/sequence filter key tracking (0% to 100%).
  • FILTER FM: Audio-rate filter cutoff modulation driven directly by the oscillator.
  • ACC DECAY: Independent accent envelope decay length control (20 ms to 500 ms).
  • SLIDE TIME: Variable portamento glide rate (10 ms to 400 ms).

🕹️ 256-Step Multi-Bank Performance Sequencer

• 4 Independent Pattern Banks (A, B, C, D): Each bank holds a full 64-step sequence (4 pages of 16 steps) for 256 total programmable steps.
• Performance Pattern Chaining (CHAIN): Quantized pattern queueing that loops the current bank until you queue the next bank to drop seamlessly on the downbeat.
• Live Background Editing: Switch between banks and tweak notes silently while the audio engine keeps playing the active bank in the background.
• Auto-Follow Playhead (FOLLOW): Automatically flips pages (1 → 2 → 3 → 4) in real-time as the sequence progresses.
• Instant Page Auditioning: Pressing RUN immediately starts playback on whichever page you are currently viewing (e.g., Page 3 starts on step 33 instantly).
• Cross-Bank Copy & Paste: Copy any 16-step page from any bank and paste it anywhere else.

🎲 Musical Scale-Aware Randomizer

• Root Key Selector: Quantize randomized basslines to any key (C through B).
• 8 Musical Scales & Modes:
  • Minor Pentatonic (Classic Acid Techno & House)
  • Natural Minor (Aeolian) (Deep melodic techno)
  • Dorian (Chicago & Detroit acid grooves)
  • Phrygian (Dark Goa & Psytrance acid)
  • Acid Blues (Tritone $\flat5$ blue note grit)
  • Major Pentatonic & Major (Ionian)
  • Chromatic (Free unquantized generation)
• Musical Weighting: Biased towards root notes (45%), fifths (25%), and octave jumps with syncopated acid rhythm templates.
• Smart Legato Slide Validation: Slides are strictly placed only when transitioning into another active note—never leaving an orphaned slide hanging into a rest.
• Page-Aware: Randomizing while on Page 1 randomizes the full sequence; randomizing while on Page 2, 3, or 4 randomizes only that specific 16-step page.

🎹 Arpeggiator & Chord Hold

• 5 Playback Modes: ARP OFF, UP, DOWN, UP-DOWN, RANDOM.
• HOLD Mode: Play a chord on your MIDI controller and lock it in. The arpeggiator will continuously cycle the chord in tempo, keeping your hands free to tweak filter and resonance knobs live.

🎚️ Integrated FX Rack

• Distortion 1: Hard-clipping distortion with input gain, level makeup, dry/wet mix, and a classic passive tilt tone filter.
• Stereo Synced Delay: Tempo-synchronized subdivisions (1/16, 1/16D, 1/16T, 1/8, 1/8D, 1/8T, 1/4, 1/4D, 1/4T, 1/2) with damping and stereo Ping-Pong mode.
• Plate Reverb: Early 90's warehouse dark plate algorithm with pre-delay, low-end cleanup (HPF), high-frequency damping (LPF), and size/decay parameters.

🎨 Customization & Preset Management

• 6 Visual LED Themes:
  • Classic Red (TB-303)
  • Acid Green
  • Cyber Cyan
  • Electric Violet
  • Solar Amber
  • Trans Pride (dual-tone pastel blue/white/pink gradient glow across all illuminated buttons)
• Human-Readable XML Presets (.s303 / .xml): Clean XML preset format saving all 256 sequence steps, synth parameters, Devil Fish mods, FX rack settings, and active theme for easy sharing.

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📦 Downloads & Installation

Pre-built binaries for Linux, macOS (Universal: Apple Silicon & Intel), and Windows are automatically generated on every release.

👉 Download the Latest Release

Formats Available:

• VST3 (64-bit plugin for your DAW of choice)
• AU (Audio Unit) (macOS)
• Standalone Application (No DAW required—run directly on your desktop with ALSA/JACK/DirectSound/CoreAudio)

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🛠️ Building from Source

Prerequisites

• CMake 3.22 or higher
• C++17 compatible compiler (gcc, clang, or MSVC)

Linux (Debian / Ubuntu / Fedora):

# Debian / Ubuntu
sudo apt-get install build-essential cmake libasound2-dev libjack-jackd2-dev \
    libgl1-mesa-dev libx11-dev libxrandr-dev libxinerama-dev \
    libxcursor-dev libfreetype6-dev libxcomposite-dev

# Fedora
sudo dnf install gcc-c++ cmake alsa-lib-devel pipewire-jack-audio-connection-kit-devel \
    mesa-libGL-devel libX11-devel libXrandr-devel libXinerama-devel \
    libXcursor-devel freetype-devel libXcomposite-devel