# Turn audio into MIDI

> Turn a sung, hummed or played part into notes you can edit and send to any instrument: how it works, what it gets wrong and what you can build with it.

Canonical: https://maru.audio/help/turn-audio-into-midi
Documentation index: https://maru.audio/help/llms.txt

Hum a bass line and hear it on a synth. Record a guitar riff and get the notes
in your piano roll. Audio to MIDI listens to a recording and writes down the
pitches, start times, lengths and loudness of the notes it hears, so the
performance can drive any instrument.

## Try it

[Pitchy](https://maru.audio/modules/pitchy) follows a single voice or instrument as you play and
sends MIDI notes as you go. Sing or play into it, and put a synth after it.

## How it works

There are two kinds of listening:

- **One note at a time.** For a voice, a whistle, a bass or a solo line, a pitch
  tracker measures how often the waveform repeats. It is fast, needs no model
  download and can run while you play.
- **Several notes at once.** For chords, piano and guitar, a trained model
  looks at the sound's spectrum and estimates every note it believes is
  sounding. It works on a recorded clip, after the fact.

Drum recordings are a third case: a drum transcriber classifies each hit as a
kick, snare, hi-hat and so on, rather than measuring pitch.
[Audio to MIDI](https://maru.audio/learn/audio-to-midi.md) in Learn explains the techniques in
more depth.

## Ideas

- **Hum your bass lines.** Sing the line you hear in your head, then play it
  back on a bass synth and fix the two notes that came out wrong.
- **Voice as a controller.** Send live pitch from your voice to an instrument
  that would otherwise need a keyboard.
- **Steal from your old recordings.** Transcribe a riff from a voice memo and
  rebuild it with new sounds.
- **Beatbox to drums.** Turn mouth percussion into a drum pattern; see
  [Beatbox to drums](https://maru.audio/learn/beatbox-to-drums.md).
- **Teach and practise.** Show a student the pitch they actually sang against
  the note they meant.

## What it gets wrong

- **Pitch is not a note.** Vibrato, slides and expressive bends are rounded to
  the nearest note, so a sung phrase can come out choppy. Expect to edit.
- **One voice works best.** Reverb, backing music or two instruments at once
  confuse the one-note tracker, and even the many-note model guesses in dense
  mixes. [Split the song into stems](https://maru.audio/help/split-a-song-into-stems.md)
  first if you can.
- **Octaves and quiet notes slip.** A note can jump an octave, and soft notes
  may be missed.
- **No notes is a real answer.** A clip of noise or unpitched sound can
  correctly return nothing.
- Clip transcription is limited to 30-second clips in the browser.

## Build your own

Remix a module that already does this in Studio, or ask your coding agent to
add it to yours:

```text
Read the Maru docs page "Audio to MIDI in a module", then read the Pitchy
module's source with `maru module files pitchy` and `maru module read`.
Add a "sing to play" input to my synth: track my voice, quantise to the
synth's scale, and keep the keyboard working as before.
```

Developers can start from [Audio to MIDI in a module](https://maru.audio/docs/audio-to-midi-in-a-module.md).
The [model directory](https://maru.audio/models) describes the transcription models.