Algorithmic Music Engine

Phase 1 Complete — Foundation

Concept

A tool for exploring composition ideas through generative algorithms. A multi-level energy model drives every musical decision — from macro-level track arc (intro, build, peak, breakdown) down to per-16th-note accent patterns — producing coherent tracks with musical tension and release.

Quick Facts


Status	Phase 1 Complete — Foundation
Language	Rust
Started	2026

Why Generative

Most music generation tools either randomize MIDI notes or stitch together pre-made loops. Neither approach produces tracks with intentional structure. This engine takes a different approach: model energy as the primary dimension, then derive all musical elements (pattern density, filter cutoff, accent placement) from that energy curve.

The result is a track that breathes — quiet sections build tension, peaks deliver density, and transitions feel intentional rather than arbitrary.

Multi-Level Energy Model

The architectural core. Energy flows from macro structure down to individual note accents:

Macro (Track Arc)
  Control-point curves: intro → build → peak → breakdown → outro
  Linear interpolation between user-defined energy waypoints

    Meso (Phrase Breathing)
      8-bar phrase patterns creating tension/release cycles
      Layered on top of macro curve

        Micro (Groove Accents)
          16th-note accent patterns for swing and syncopation
          Drives velocity and timing variations

          Sub-Channels (Per-Element)
            Each element (kick, bass, hat, clap) has independent:
            - Energy threshold (when it activates)
            - Response curve (how it scales with energy)
            - Attack time (how quickly it responds)

Sound Design

Phase-accumulating oscillators, biquad filters, and amplitude envelopes:

Kick: Sine oscillator with pitch envelope (150 Hz → 50 Hz) plus a click transient for attack definition
Bass: Sawtooth oscillator through a biquad lowpass filter with energy-driven cutoff modulation
Hi-hats: Noise through a highpass filter — closed at 7 kHz with 30 ms decay, open at 6 kHz with 150 ms decay
Clap: Multi-tap noise (3 bursts) through highpass filter, mimicking multiple hands

Pattern Generation

Patterns respond to the energy model rather than following fixed sequences:

Kick: Scales from 2-beat patterns at low energy through 4-on-the-floor to ghost 16th notes at peak
Bass: Rolling 16th-note patterns with density proportional to energy level
Hi-hats: Off-beat syncopation with closed/open variation driven by accent patterns
Clap: Enters on beats 2 and 4 when energy exceeds a configurable threshold

Mood Presets

Five presets, each defining a key, scale, energy curve shape, and filter range:

Mood	Key	Scale	Character
Dark	D	Phrygian	Dark, driving
Mysterious	C#	Phrygian Dominant	Goa trance exotica
Euphoric	E	Lydian	Bright, uplifting
Melancholy	C	Harmonic Minor	Sad tension
Aggressive	D#	Minor	Hard, driving

Usage

# Algorithmic Music Engine
cargo run

# Algorithmic Music Engine
cargo run -- --bpm 145 --bars 64 --mood euphoric --output track.wav

# Algorithmic Music Engine
cargo run -- --seed 42 --output reproducible.wav

# Algorithmic Music Engine
cargo run -- --key D2 --scale phrygian

Without --output, the engine launches an interactive TUI with real-time playback, energy visualization, and pattern display.

Output

16-bit stereo WAV at 44.1 kHz
Soft-clip limiter (tanh normalization to -0.5 dB)
Constant-power stereo panning
Full tracks render in under 30 seconds

Roadmap

Phase 1: Foundation (Complete) Core synthesis, energy model, pattern generation, WAV export, TUI playback.

Phase 2: Effects & Mix (Planned) Reverb, delay, sidechain compression, EQ. Using fundsp for the effects chain.

Phase 3: Interactive Energy Editing (Planned) TUI with draggable control points for energy curves, real-time parameter adjustment.

Phase 4: Musical Evolution (Planned) Key changes, acid lines (303-style sequencing), pattern mutation over time.

Phase 5: Sample Integration (Planned) Load external sample packs, time-stretching, pitch-shifting, hybrid synthesis.

Phase 6: Browser UI (Planned) WASM-based browser interface with spectrum analyser and waveform display.

Tech Stack

Language: Rust
DSP: Phase-accumulating oscillators, biquad filters, amplitude envelopes (f64 internal precision)
Effects (Phase 2+): fundsp
WAV Export: hound
CLI: clap 4
Playback: cpal (real-time audio)
TUI: ratatui + crossterm
RNG: Seeded rand for reproducible generation

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