# A practical look at mp3tomidi — MIDI to audio with piano, synth, or FM

Render a MIDI file through three oscillator instruments in the browser. Choose piano (triangle), synth (sawtooth), or FM (modulated sine, described as similar to a Rhodes), then download WAV or another format.

## What it is

If you need to hear a MIDI file and do not have a sampler loaded, https://mp3tomidi.art/midi-to-audio/ renders note-on and note-off events with three oscillator presets: piano (triangle waves), synth (sawtooth), and FM (sine with frequency modulation, described as similar to a Rhodes). This is not sampled VST playback, and the site says the result will differ from professional instrument libraries. Control changes, program changes, and SysEx are not rendered. WAV is synthesized in the browser at 44.1 kHz stereo; other formats use a cached ffmpeg WebAssembly encoder of about 32 MB on first use. For Format 1 files, notes from the first track are used. More is available at [MIDI to audio converter](https://mp3tomidi.art/midi-to-audio/). Open https://mp3tomidi.art/ in your browser.

The focus here is MIDI to Audio. oscillator preview of a MIDI file The same site also includes related browser tools for tempo, chords, stems, MIDI editing, and sheet-music drafts.

## Key features

- A 6-stem splitter runs a client-side HT-Demucs model (vocals, drums, bass, guitar, piano, and other). The first visit downloads about 147 MB of weights.
- Sheet-music tools build a MusicXML 3.1 draft from MIDI or from audio, which you can finish in MuseScore or a similar app.
- Core tools are free, with no signup and no credit card, and they run in Chrome, Firefox, Safari, and Edge.
- The BPM and key finder typically reports tempo within 1–2 BPM on steady-tempo tracks, with a confidence score, using the Web Audio API.
- MP3 and other audio can be turned into a Standard MIDI Type 0 file with a piano-roll preview, using Spotify's Basic Pitch model in the browser.
- MIDI to audio can render the first track of a Format 1 file with piano, synth, or FM oscillator sounds to WAV in the browser, or to other formats with a cached ffmpeg WebAssembly encoder.
- A MIDI editor lets you change pitch, timing, and velocity on a piano roll, with undo, then download a Standard MIDI file.

## How to use it

1. Open https://mp3tomidi.art/ and pick the tool you need, such as MP3 to MIDI, BPM and key, chords, stems, the MIDI editor, or sheet music.
2. Load an audio or MIDI file in the browser. Most tools process the file on your device.
3. Review the preview: a piano roll for transcription, a tempo and key reading, a chord list, or separated stems.
4. Edit notes if you need to, then download MIDI, audio, CSV, or MusicXML.
5. Check the result by ear or in your DAW; these outputs are drafts for reference, not finished professional transcriptions.

## Use cases

- **Musicians:** Turn a practice take into editable MIDI notes.
- **Producers:** Sketch a melody or split a reference mix into stems before arranging.
- **DJs:** Check BPM and key on a track without installing a desktop app.

## Honest limits

- The free MP3-to-MIDI conversion covers only the first 30 seconds of a file, not the whole track.
- Results are drafts for reference, not professional transcriptions; dense mixes may need a stem split first, and every transcription should be checked by ear.
- Core tools are free with no signup and no credit card; do not expect a published paid checkout on the public site.
- MIDI-to-audio uses oscillator sounds, not sampled VSTs.
- The site does not advertise a public API, and it is not a full DAW replacement.
- The stem splitter is a local HT-Demucs build, not an official Meta Demucs service, and the first visit downloads a large model.
- The MIDI-to-sheet preview is read-only; finish the score in another notation app.

## Summary

mp3tomidi is a free browser toolkit for MP3 to MIDI conversion and related music tools. It is most useful when you treat the output as a draft and stay within the limits above. Open https://mp3tomidi.art/ in your browser.