1
# A practical look at mp3tomidi — Local HT-Demucs, not a cloud upload
3
The live stem page runs htdemucs_6s in your browser sandbox. Unlike older server-side descriptions, the current stem tool downloads model weights once and keeps your audio on the device, using WebGPU or CPU.
7
Privacy-minded users should follow the live stem page, not older one-line summaries. https://mp3tomidi.art/stem-splitter/ says inference runs entirely in the browser sandbox and that audio and output stems are never uploaded or stored remotely. It is a client-side HT-Demucs v4 (htdemucs_6s) port, with WebGPU acceleration or CPU fallback. The page also states it is not an official Meta Demucs service and is not hosted or endorsed by Meta. First use downloads about 147 MB of weights. If a job fails, the FAQ suggests enabling hardware acceleration, closing heavy tabs, or trimming the file under 50 MB and 10 minutes. More is available at [6-stem splitter](https://mp3tomidi.art/stem-splitter/). Open https://mp3tomidi.art/ in your browser.
9
If you came for Stem Splitter, that is the tool this note emphasizes. privacy-first local stem separation You can still move to the other free tools on the same site without creating an account.
13
- The free MP3-to-MIDI conversion transcribes the first 30 seconds of a file; uploads may be up to 50 MB and from 1 second to 10 minutes long.
14
- 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.
15
- Core tools are free, with no signup and no credit card, and they run in Chrome, Firefox, Safari, and Edge.
16
- 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.
17
- Chord detection labels nine qualities across twelve roots, plus N/C, and can export a CSV of timings and confidence.
18
- Sheet-music tools build a MusicXML 3.1 draft from MIDI or from audio, which you can finish in MuseScore or a similar app.
19
- 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.
20
- A MIDI editor lets you change pitch, timing, and velocity on a piano roll, with undo, then download a Standard MIDI file.
24
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.
25
2. Load an audio or MIDI file in the browser. Most tools process the file on your device.
26
3. Review the preview: a piano roll for transcription, a tempo and key reading, a chord list, or separated stems.
27
4. Edit notes if you need to, then download MIDI, audio, CSV, or MusicXML.
28
5. Check the result by ear or in your DAW; these outputs are drafts for reference, not finished professional transcriptions.
32
- **DJs:** Check BPM and key on a track without installing a desktop app.
33
- **Producers:** Sketch a melody or split a reference mix into stems before arranging.
34
- **Musicians:** Turn a practice take into editable MIDI notes.
38
- Core tools are free with no signup and no credit card; do not expect a published paid checkout on the public site.
39
- The site does not advertise a public API, and it is not a full DAW replacement.
40
- The free MP3-to-MIDI conversion covers only the first 30 seconds of a file, not the whole track.
41
- The stem splitter is a local HT-Demucs build, not an official Meta Demucs service, and the first visit downloads a large model.
42
- The MIDI-to-sheet preview is read-only; finish the score in another notation app.
43
- Results are drafts for reference, not professional transcriptions; dense mixes may need a stem split first, and every transcription should be checked by ear.
44
- MIDI-to-audio uses oscillator sounds, not sampled VSTs.
48
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.