Supported formats and limits
There is no list of blessed file types. Damper converts whatever you upload into the form the transcription needs, so the rule is simple: if it contains audio, it will almost certainly be read.
Audio files
MP3, WAV, FLAC, M4A, AAC, OGG, Opus, WMA, AIFF and AIF all work. Lossless files carry more detail than compressed ones, but the difference matters far less than the recording itself: a clean MP3 of a well-recorded piano beats a lossless file of a muddy one.
Video files
MP4, MOV, MKV and WebM work too. The audio track is extracted and the picture is discarded. This is the usual route for a piano performance filmed on a phone.
Limits
| Length | 15 minutes per file. Longer recordings are refused with a message telling you the actual length. |
|---|---|
| Size | 95 MB. Long WAV files hit this before the length limit; converting to MP3 or FLAC first solves it without losing anything that matters. |
| Time | A four-minute piece takes about two minutes to transcribe. |
| Storage | Your upload and the resulting MIDI are deleted after 24 hours. See the privacy page. |
What you get back
One standard MIDI file: type 0, a single track, containing the notes, their timing, a velocity for each note and the sustain pedal written as CC64. It opens in any DAW, sampler or notation editor.
No PDF and no MusicXML. Damper produces a performance you can edit, not a score you can print.
What gets refused, and why
- Files with no readable audio. A document renamed to .mp3, or a video with no sound track.
- Recordings over 15 minutes. Split them and upload the parts.
- Silence, or near-silence. If there is nothing to transcribe you are told so rather than handed an empty file.
Note what is not on that list. Damper does not refuse a piano recording for being difficult, noisy, historic or oddly tuned. If the transcription looks weak, it says so and still gives you the file, because whether it is useful is your call and not ours.
What is outside the design
Damper reads solo piano. Piano with vocals, strings, drums or a backing track will produce something, but the other instruments get turned into piano notes and the result is rarely worth editing. If your piano is inside a full mix, separate the stems first and upload the piano stem on its own. Other keyboard instruments — electric piano, harpsichord, organ — are outside what the transcription was trained on.
Transcribe a recording