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Music Programming Language ​

DifficultyAdvanced
Team Size2-3 people
Time~30-35 hours
Demo-ready byStep 5
PrerequisitesJavaScript, basic music theory, compiler/interpreter concepts
Built bySonic Pi, TidalCycles, ChucK, Alda

Skills you'll earn: Lexer/parser design, DSL implementation, Web Audio API, live coding, MIDI export

Start with playing a note from text. End with a DSL that composes music.

(Assumes basic JS knowledge; parser theory and music concepts learned along the way)

Step 1: Parse a note and play it (~2 hours) ​

You want to type play C4 and hear a C note.

  • Build a simple parser that reads a line of text and extracts the command and arguments
  • Use the Web Audio API to create an oscillator at the correct frequency
  • Map note names to frequencies (A4 = 440 Hz, use the equal temperament formula)
  • Build a text input and a "Run" button

You now have: A one-command music interpreter.

Step 2: Sequences and duration (~2-3 hours) ​

play C4 plays one note. You want play C4 D4 E4 to play a melody.

  • Extend the parser to accept multiple notes on one line
  • Add duration syntax: C4:q (quarter note), C4:h (half), C4:e (eighth)
  • Schedule notes sequentially using AudioContext.currentTime
  • Add a tempo 120 command to set BPM

You now have: A sequential note language.

Step 3: Define a formal grammar (~4-5 hours) ​

String splitting breaks on edge cases. You need a real parser.

  • Define a grammar for your language using PEG.js or write a recursive descent parser by hand
  • Support statements: tempo, play, rest, repeat
  • Parse into an AST (Abstract Syntax Tree) — an array of node objects
  • Walk the AST to schedule audio

You now have: A parsed language with an AST.

Step 4: Variables and patterns (~3-4 hours) ​

You're repeating the same sequence everywhere. You want to name it.

  • Add variable assignment: riff = C4:q D4:q E4:q
  • Add pattern playback: play riff
  • Support repeat 4 { riff } for looping
  • Variables are stored in a symbol table during interpretation

You now have: Reusable musical patterns.

Step 5: Multiple tracks (~3-4 hours) ​

One melody line is thin. You want drums and bass playing simultaneously.

  • Add track syntax: track bass { ... } and track drums { ... }
  • Each track gets its own oscillator or sound source
  • Tracks play in parallel (schedule all tracks from the same start time)
  • Add instrument selection: instrument sine, instrument square, instrument sawtooth

You now have: Multi-track composition.

Step 6: Chords and dynamics (~3 hours) ​

  • Add chord syntax: [C4 E4 G4]:h plays three notes simultaneously
  • Add velocity/volume: C4:q@0.8 plays at 80% volume
  • Support crescendo and decrescendo over a range of notes

You now have: Expressive music notation.

Step 7: A code editor with live preview (~3-4 hours) ​

  • Build a CodeMirror editor with syntax highlighting for your language
  • Add a "Play" button and a "Stop" button
  • Show errors inline (highlight the line with the parse error)
  • Add a piano roll visualization of the output

Step 8: Export (~3-4 hours) ​

  • Export as MIDI using a library like jsmidgen or midi-writer-js
  • Export as WAV by recording the Web Audio output
  • Export the source code as a .music file

Step 9: Standard library (~3-4 hours) ​

  • Ship built-in patterns: drum loops, common chord progressions, scales
  • Let users import community-shared patterns
  • Add a package system: import jazz-chords

Useful Resources ​

Where to go from here ​

  • Live coding mode (change code while music plays, hot-reload)
  • Visual block-based editor (Scratch-style) that generates the DSL
  • Microtonal support (custom tuning systems)
  • Integration with external MIDI devices
  • Collaborative jam sessions over WebSocket