DEV Community

mycute
mycute

Posted on

AI in a MIDI file: the model is the notes

#showdev #opensource #webdev #ai

AI in a MIDI file: the model is the notes

The QR put the model in a URL. The favicon put it in pixels. The PDF put it in /Keywords.
This one puts it in note-on events.

The file is 4,493 bytes. The model is the same 160-word SMS spam classifier, 1,579
bytes of int8 weights, 93.54% on 1,115 held-out SMS. It is packed into 1,053 note-on
events: each event carries two ASCII characters, one in the note byte and one in the
velocity byte. Together they are the base64url JSON of the model.

midi.html parses the MIDI track, rebuilds the string and classifies. The first 128 notes
are playable. The tune is the bytes.

The size accounting

artifact bytes
model JSON 1,579
MIDI 4,493
overhead (events, text meta, header) 2,914
QR URL 2,158
favicon PNG 1,519
WAV 1,627
PDF 3,832
SVG 5,004

The MIDI is larger than the QR/PNG/WAV because each base64 character becomes a note event
with a status byte and a delta byte. It is still small enough to email or commit.

What is in the file

The track has five text meta events:

  • the title and the model description;
  • the measured accuracy;
  • a pointer to the viewer;
  • SHA256:<64 hex>.

Then 1,053 note-on events. The text meta events are readable in any MIDI tool; the note
events are the payload. The header is format 0, one track, 96 ticks per quarter note.

The page parses the events, collects String.fromCharCode(note, velocity) pairs, base64
decodes them and runs the int8 Complement NB. No server.

Why a MIDI?

Because it is an event file that every DAW and player already understands. It is not a
rendered audio file; it is a sequence of events. The model travels in the event stream,
and the file can still be opened and played. A MIDI renderer turns the notes into sound and
throws the note bytes away — which is exactly the container trade.

It is also a good stress test for the parser: variable-length delta times, meta events,
running status, note-on/velocity. The file is small; the code is ordinary.

What this is not

  • Not an audio model. The MIDI is not a voice or a song; it is data that can be played.
  • Not a security proof. The note events are inspectable. A MIDI file is a lossless event container, not obfuscation. The SHA-256 is integrity, not a signature.
  • Not robust to a DAW export. A tool that quantizes, transposes, or renders to WAV can change or drop the events. A byte copy is safe; a musical edit is not.
  • Not a production spam filter. One 80/20 split, 1,115 SMS, one machine.

The ladder now

  • SMS int8: 1,579 bytes, 93.5% on 1,115 rows;
  • QR URL: 2,158 bytes;
  • favicon: 1,519 bytes;
  • WAV: 1,627 bytes;
  • PDF: 3,832 bytes;
  • SVG: 5,004 bytes;
  • MIDI: 4,493 bytes;
  • 130 KB AG News coreset: a 178,761-byte PDF;
  • 1.7 MB linear model: 88.5% embedded / 91.0% fresh;
  • 5 MB adapter on a shared 4-bit base.

The behavior is the same. The container changes what travels with it and which tool can
destroy it.

Top comments (0)