Boomie

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|/ \___/ (_______)(_______)|/     \|\_______/(_______/

Real-time music synthesizer and composition engine written with dynamic playback control and advanced audio effects. Designed for on the fly compositing.

Why

Boomie is made for the Liefde. game engine. The main reason for including a music synthesizer in a game engine is to enable dynamic control over the soundtrack. Of course this module can be used outside the context of a videogame, which is why I released it as a seperate crate.

Features

Audio Synthesis

• Waveform types: Sine, Square, Triangle, Sawtooth, and Noise
• Sample based playback: Load and play WAV files with pitch adjustment and interpolation
• ADSR envelope shaping: Full Attack, Decay, Sustain, Release control per instrument
• Real-time synthesis: Low-latency audio output using cpal
• Chord support: Play multiple notes at once
• Pitch slides: Smooth pitch transitions between individual notes
• Per-note parameters: Individual pan and slide control for each note

Effects Processing

• Reverb: Freeverb based algorithm with room size, damping, wet/dry mix, and stereo width controls
• Delay: Configurable delay time, feedback, and wet/dry mix with feedback loop
• Distortion: Waveshaping distortion with drive, tone control (lowpass filtering), and wet/dry mix
• Filters: Biquad filters supporting lowpass, highpass, and bandpass modes with cutoff and resonance control
• Effects chain: Process audio through multiple effects in sequence

Dynamic Playback Control

• Real-time parameter adjustment: Change volume, pitch, and track states during playback
• Crossfading: Smooth transitions between different arrangements
• Track muting: Enable/disable individual tracks on the fly
• Looping: Support for arrangement level and track level loop points
• Fade in/out: Automatic fade envelopes for arrangement start and end
• Master controls: Global volume and pitch adjustment
• Parameter interpolation: Gradual volume changes over time

Installation

Add Boomie to your Cargo.toml:

[dependencies]
Boomie = "0.1.2"

Or add via cargo:

cargo add Boomie

Example

use boomie::*;
use std::error::Error;

fn main() -> Result<(), Box<dyn Error>> {
    let mut engine = SynthEngine::new()?;
    
    // Load samples
    engine.load_sample("kick", "samples/kick.wav")?;
        
    // Play arrangement
    let arrangement = engine.load_arrangement("songs/song.bmi")?;
    engine.play_arrangement(arrangement)?;
    engine.set_loop_enabled(true);
    
    engine.set_master_volume(0.8);
    engine.set_track_volume("bass", 1.2);
    std::thread::sleep(std::time::Duration::from_secs(30));
    engine.stop();
    
    Ok(())
}

API

Core Functions

Playback Control

Dynamic Parameters

File Format Reference

Melody File (.mel)

Metadata

Instrument Configuration

ADSR Envelope

Sequence Elements

Notes:

note: PITCH, DURATION, VELOCITY [, PARAMS...]

Chords:

chord: NOTE1+NOTE2+NOTE3, DURATION, VELOCITY

Rests:

rest: DURATION

Silence for specified duration in beats.

Effects

Example

name: bass
tempo: 120
waveform: sawtooth
volume: 0.9
attack: 0.01
decay: 0.2
sustain: 0.7
release: 0.3
pan: -0.3

note: C2, 1.0, 0.8
note: E2, 0.5, 0.9, slide=G2
chord: C2+E2+G2, 2.0, 0.7
rest: 0.5

filter: lowpass, 800, 0.5
reverb: 0.3, 0.4, 0.2, 0.9

Bundles Music Index files/Arrangements (.bmi)

Metadata

Tracks

track: MELODY_FILE, START_TIME [, OVERRIDES...]

Track Override Parameters

Example

name: Song
master_tempo: 120
fade_in: 2.0
fade_out: 3.0

track: bass.mel, 0.0, volume=1.2
track: melody.mel, 2.0, pitch=1.0, reverb=0.6:0.5:0.3:1.0
track: drums.mel, 4.0, filter=lowpass:800:0.5
track: kick.mel, 8.0, dist=3.0:0.8:0.7, pan=0.3

loop: 0.0, 16.0

Note Parsing

Notes follow standard music notations:

Frequency calculation:

• Base frequencies start at C0 = 16.35 Hz
• Each semitone multiplies by 2^(1/12)
• Each octave doubles the frequency

Details

Audio Engine

Effects Implementation Details