🎹 Music Factory

Pick a famous song. Watch it light up note-by-note. Hear it. Download the .mid.

No build, no server, no account. Two HTML files, vanilla JS, Web Audio.

Open the apps

• [[factory/index|🎛️ Factory — multi-song MIDI player]] ← the main one. A song picker with eight public-domain classics, a piano-roll visualizer, Web Audio playback, and a one-click .mid download for every song.
• [[still-alive/index|🟠 Still Alive — Portal player]] — the dedicated, hand-authored Portal "Still Alive" experience. Same player engine, GLaDOS-themed.

Songs in the factory

Song	Composer / source
Ode to Joy	Beethoven, Symphony No. 9 (1824)
Für Elise	Beethoven, Bagatelle No. 25 in A minor
Twinkle Twinkle Little Star	Trad. / Mozart variations
Jingle Bells	James Lord Pierpont, 1857
Happy Birthday to You	Patty & Mildred Hill, 1893 (PD since 2016)
Korobeiniki (Tetris Theme A)	Russian folk, 1861
Canon in D	Pachelbel, c. 1680
When the Saints Go Marching In	Traditional spiritual
In the Hall of the Mountain King	Grieg, Peer Gynt (1875)
Greensleeves	English traditional, 16th c.
Frère Jacques	French traditional, c. 1780
Auld Lang Syne	Robert Burns, 1788
Amazing Grace	John Newton, 1779
William Tell Overture (Finale)	Rossini, 1829
Hava Nagila	Jewish traditional
Yankee Doodle	American traditional, c. 1750s

All public-domain. The .mid files are generated on the fly from the in-page note data — no audio files or external requests.

Want a new song?

Open the Tasks panel and ask: "add my favorite MIDI song — "

That kicks off an agent task that:

1. Looks up or transcribes the melody (and a simple bass line) into the cabinet's note format
2. Verifies the song is public-domain or your original work
3. Appends it to the SONGS array in factory/index.html
4. Reloads the factory so the new song appears in the picker

If you'd rather hand-author it, the format is dead simple — see the SONGS array near the top of factory/index.html. Each song is a list of ["pitchName", beats] tuples for melody (and optionally bass), plus bpm and metadata. Beats are quarter-note counts: 1 is a quarter, 0.5 an eighth, 1.5 a dotted quarter, 2 a half. "rest" for silence.

Keyboard shortcuts (in the factory)

• Space — play / pause
• R — restart current song
• ← → — previous / next song

What's under the hood

Single-file factory/index.html, ~600 lines:

• Compiler — turns [pitch, beats] tuples into absolute-time note events
• Web Audio synth — sine + triangle (melody) / sine + sawtooth (bass), per-note ADSR
• Canvas piano roll — color-coded melody/bass, scrolling playhead window
• Standard MIDI File writer — emits format-1 .mid binary by hand: header chunk, MTrk chunk, tempo + time-sig + program-change + delta-timed note-on/note-off events. The download is a real, DAW-importable file.

No dependencies. Runs offline. Open factory/index.html directly in any modern browser.