# A practical look at mp3tomidi — BPM, key, and chords as one analysis pass

This page is a straightforward look at mp3tomidi, a free MP3 to MIDI and audio toolkit. Use the BPM and key finder plus chord detection on the same file to collect tempo, key, and a timestamped progression, all locally in the browser.

## What it is

Sometimes you do not need MIDI yet — you need to understand the record. On https://mp3tomidi.art/ you can run the BPM and key finder and the chord detector on the same upload family of formats (up to 50 MB, 1 second to 10 minutes). One page gives a dominant tempo, a major or minor key, and confidence; the other gives a progression with nine chord qualities and a CSV export. Both are described as local Web Audio API processing with no login. If you later want notes or a score, add the converter or the sheet-music tools. All of it is still a draft to check by ear. You can read more in [BPM and key finder](https://mp3tomidi.art/bpm-key-detection/). Start from https://mp3tomidi.art/.

If you came for BPM & Key Detection, that is the tool this note emphasizes. combined tempo, key, and chords You can still move to the other free tools on the same site without creating an account.

## Key features

- Sheet-music tools build a MusicXML 3.1 draft from MIDI or from audio, which you can finish in MuseScore or a similar app.
- A MIDI editor lets you change pitch, timing, and velocity on a piano roll, with undo, then download a Standard MIDI file.
- 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.
- 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.
- 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.
- Chord detection labels nine qualities across twelve roots, plus N/C, and can export a CSV of timings and confidence.
- 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.

## 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

- **Producers:** Sketch a melody or split a reference mix into stems before arranging.
- **Musicians:** Turn a practice take into editable MIDI notes.
- **Students:** Get a first-draft score or chord list from a recording.

## Honest limits

- The MIDI-to-sheet preview is read-only; finish the score in another notation app.
- The site does not advertise a public API, and it is not a full DAW replacement.
- 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 stem splitter is a local HT-Demucs build, not an official Meta Demucs service, and the first visit downloads a large model.
- 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.

## 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. Start from https://mp3tomidi.art/.