# ChromaFlock

![ChromaFlock](logo.png)

A subtractive synthesizer plugin built with [JUCE](https://juce.com). macOS (VST3, AU, Standalone) and Linux (VST3, Standalone).

## Overview

ChromaFlock is a fully-featured subtractive synthesizer with dual oscillators, multi-mode filter, dual LFOs, two envelopes, and a complete effects chain. All DSP is custom - no external audio libraries. 55 automatable parameters, 16-voice polyphony, 27 built-in presets, and a real-time visual interface with waveform display, spectrum analyzer, VU meter, and interactive piano keyboard.

## Obligatory AI notice

Chromaflock was coded with the assistance of an AI coding agent. If that's a problem for you, please kindly just use a different synthesizer.

## Screenshot

![ChromaFlock Screenshot](shot.png)

## Signal Flow

```
Osc1 + Osc2 → Amp Envelope × Velocity → Filter → Drive → Distortion → Compression → Auto-Pan → Delay → Reverb → Output
```

## Oscillators

Two independent oscillators per voice, each with:

- **17 waveforms**: Sine, Saw, Square, Triangle, Noise, Pulse 25%, Pulse 12%, Rev Saw, Full Rect, Half Rect, Stair 4, Stair 8, Soft Sine, Sinc, Exp Pulse, Double Sine, SuperSaw
- **Octave shift**: -3 to +3
- **Semitone shift**: -12 to +12
- **Fine tune**: ±100 cents
- **Level**: 0.0 – 1.0
- **Phase offset** (OSC 2): 0.0 – 1.0 for detuned/synced phase relationships
- **Stereo panning**: Equal-power pan law per oscillator, summed additively

## Filter

TPT (Topology-Preserving Transform) SVF - stable, alias-free, modulation-friendly. Two independent filter instances per voice for proper L/R stereo processing.

- **5 types**: Low-Pass 12dB, Low-Pass 24dB, Band-Pass, High-Pass, Notch
- **Cutoff**: 25 Hz – 20 kHz (logarithmic)
- **Resonance**: 0.0 – 1.0
- **Envelope amount**: Modulates cutoff via filter envelope (±4 octave range)
- **Key tracking**: Cutoff follows pitch, 0% – 100%

## Envelopes

Two independent ADSR envelopes per voice - one for amplitude, one for filter modulation:

| Parameter | Range |
|-----------|-------|
| Attack    | 0.001s – 5.0s (log) |
| Decay     | 0.001s – 5.0s (log) |
| Sustain   | 0.0 – 1.0 |
| Release   | 0.001s – 10.0s (log) |

Linear ramp shape. Both envelopes reset per-note.

## LFOs

Two independent LFOs per voice, each with:

- **4 shapes**: Sine, Triangle, Saw, Square
- **Rate**: 0.05 Hz – 20 Hz (log)
- **Depth**: 0.0 – 1.0
- **4 destinations**: Filter Cutoff, OSC1 Pitch, OSC2 Pitch, Both OSCs
- Phase resets on note-on
- Pitch modulation range: ±12 semitones

## Arpeggiator

Tempo-synced arpeggiator that sequences held notes into rhythmic patterns. Pure note-logic - no audio path changes.

- **On/Off**: Enables the arpeggiator and routes incoming MIDI notes through it
- **7 patterns**: Up, Down, UpDown, DownUp, Random, As Played, Chord
- **Octaves**: 1 – 3 (extends the pitch pool above or below the root, clamped to MIDI range)
- **Direction**: Up or Down for octave extension
- **Rate**: 1/16, 1/8, 1/4, 1/2, 1, 2 (note-value divisions, tempo-synced via BPM)
- Tracks held notes in press order (used by the As Played pattern)

## Effects Chain

All effects are stereo and processed in series after the synth voice.

### Distortion

- **4 types**: Soft Clip (tanh), Hard Clip, Foldback (wave-folding), Overdrive
- **Amount**: 0.0 – 1.0 (drives input gain 1x – 10x)
- **Mix** (dry/wet): 0.0 – 1.0
- Bypassed when amount < 0.001

### Compression

- **Threshold**: -60 dB – 0 dB
- **Ratio**: 1:1 – 20:1
- **Attack**: 0.1 ms – 100 ms
- **Release**: 10 ms – 1000 ms
- **Makeup gain**: 0 – 24 dB
- **Mix** (dry/wet): 0.0 – 1.0
- Feed-forward envelope detector with separate attack/release time constants

### Auto-Pan

- Sinusoidal LFO panning
- **Rate**: 0.05 Hz – 20 Hz
- **Depth**: 0.0 – 1.0
- Bypassed when depth < 0.001

### Delay

- **Time**: 10 ms – 1000 ms
- **Feedback**: 0.0 – 0.95
- **Ping-pong mode**: Cross-channel feedback for bouncing stereo echoes
- **Spread**: 0.25 – 0.75 (secondary tap time)
- **Mix** (dry/wet): 0.0 – 1.0
- Dual-tap mode when ping-pong is off (wider stereo image)

### Reverb

- **Room size**: 0.0 – 1.0
- **Damping**: 0.0 – 1.0
- **Mix** (wet/dry): 0.0 – 1.0
- Fixed stereo width at 0.8

## Master

- **Pan**: Full left – Full right
- **Drive**: 1x – 5x (tanh soft clipping per-voice, normalized)
- **Master Level**: 0.0 – 1.0
- **Pitch Bend Range**: 1 – 12 semitones

## Voices

- **16-voice polyphony**
- Velocity-sensitive amplitude
- Per-sample rendering for smooth modulation
- Denormal protection (`ScopedNoDenormals`)
- All 55 parameters pushed to all voices every block

## Presets

73 built-in presets across 15 categories:

| Category | Presets |
|----------|---------|
| Init | Init |
| Bass | Sub Bass, Reese Bass, Acid Bass, Pluck Bass, Moog Bass, Gritty Bass, FM Bass, Concrete Jungle, Thunder Bass, Dystopian Bass, 808 Subblast |
| Lead | Sync Lead, Square Lead, Soft Lead, Saw Lead, Neon Rider, Champagne Supernova, Quantum Lead, Electric Sheep |
| Pad | Warm Pad, Glass Pad, Dark Pad, Shimmer Pad, Evolving Pad, Choir Pad, Infinite Horizon, Liquid Gold, Apocalypse Now |
| Keys | Electric Piano, Organ, Clav, Rhodes, Bell Keys, Toy Piano |
| FX1 | Wobble, Distorted Lead, Auto-Pan Spread, Filtered Noise |
| FX2 | Dub Delay, Reverse Reverb, Laser Zap, Space Drone, Ring Mod, Glitch Stutter |
| FX | Pirate Radio, Vapor Trail, Sugar Rush, Fleshlight |
| Insanity | Alien Swarm, Nuclear Siren, Death Ray, Toxic Waste, Broken Radio, Flesh Wound, Junkyard Dog, Pixel Storm, Venom, Screaming Eagle |
| Textures | Frozen Lake, Volcanic Ash, Iron Lung, Ghost Whisper, Cosmic Dust, Neon Dreams, Underwater, Zen Garden, Synthetic Breath |
| Chiptune | Power Up, Boss Fight, Coin Drop, 16-Bit Blast, Game Over |
| Cinematic | Space Station, Tornado Siren, Black Hole, Molten Core, Thunder Roll, Haunted Mansion, Ancient Machine |

Preset menu accessible from the PRESET button (top-left). Each preset stores all 55 parameters.

## UI

Custom dark theme with gold accents. ~50 knobs across 9 sections.

### Sections

| Section | Controls |
|---------|----------|
| OSC 1 | Waveform selector, Octave, Semi, Fine, Level knobs |
| OSC 2 | Waveform selector, Octave, Semi, Fine, Level, Phase knobs |
| Filter | Type selector, Cutoff, Resonance, Env Amount, Key Tracking knobs |
| AMP ENV | Attack, Decay, Sustain, Release knobs |
| FILTER ENV | Attack, Decay, Sustain, Release knobs |
| Master | Pan, Drive, Level, PB Range knobs |
| Distortion | Type selector, Amount, Mix knobs |
| Compression | Threshold, Ratio, Attack, Release, Makeup, Mix knobs |
| Auto-Pan | Rate, Depth knobs |
| LFO 1/2 | Rate, Depth knobs, Shape and Destination selectors |
| Delay | Time, Feedback, Mix knobs, Ping-Pong selector, Spread knob |
| Reverb | Size, Damping, Mix knobs |
| Arpeggiator | On, Pattern, Octaves, Direction, Rate selectors |

### Visualizers

- **VU meter**: RMS + peak level, green-to-red gradient, 30 fps
- **Waveform display**: Real-time from 1024-sample ring buffer, green gradient, 30 fps
- **Spectrum analyzer**: 2048-point FFT, 48-bar log frequency display, Hamming window, 30 fps
- **Piano keyboard**: Interactive C3–C7 (49 keys), click/drag to play, gold highlight on press
- **Pitch bend strip**: Vertical drag control on left side of keyboard, resets to center on release

### Scaling

UI scaling: 100%, 125%, 150%, 200% via dropdown (top-right). Window resizes proportionally.

## Parameters

55 total parameters, all DAW-automatable and saved with session state via APVTS XML serialization.

## Building

Requires JUCE (drop the framework into `./JUCE/`). Then:

```bash
make            # Build Release (VST3/Standalone; +AU on macOS)
make debug      # Build Debug
make clean      # Remove build directory
make rebuild    # Clean + build
make run        # Build and launch Standalone app
make install    # Install VST3 to system dir
```

Or directly with CMake:

```bash
cmake -B build -DCMAKE_BUILD_TYPE=Release
cmake --build build --config Release -j$(nproc)
```

Output: `build/ChromaFlock_artefacts/Release/VST3/ChromaFlock.vst3`

On macOS, plugins auto-copy to `~/Library/Audio/Plug-Ins/`. On Linux, run `make install` to copy to `~/.vst3/`.

## Tech

- **Language**: C++17
- **Framework**: JUCE 8
- **DSP**: All custom - no external audio libs
- **Filter**: TPT SVF (Topology-Preserving Transform State Variable Filter)
- **Build**: CMake + Makefile wrapper
- **Platform**: macOS, Linux

## License

Copyright (C) 2026 Armin Jenewein, <a@bsd.pm>

ChromaFlock is free software: you can redistribute it and/or modify it under the
terms of the GNU Affero General Public License as published by the Free Software
Foundation, either version 3 of the License, or (at your option) any later version.

ChromaFlock is built on the [JUCE](https://juce.com) framework, whose modules are
used here under the terms of the AGPLv3. Because AGPLv3 is a copyleft license,
ChromaFlock as a whole is distributed under the AGPLv3 to remain compliant.

This program is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE. See the GNU Affero General Public License for more details.

See the [LICENSE](LICENSE) file for the full license text.

