Convert MIDI files to WAV, MP3 or OGG locally - real synthesis in your browser with General MIDI sounds, no upload.
Running locally on your device ...
Running locally on your device ...
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No re-upload neededThese tools accept .MP3 - your file is handed over directly.
No. Everything runs in your browser - your file never leaves your device. How this is verifiable
A MIDI file contains no recorded music at all, only note and instrument instructions - which key is pressed when, for how long, and how hard. Without a synthesizer that turns those instructions into real sound, a MIDI file cannot simply be played back like an MP3 or WAV. This tool renders the whole file locally into real audio.
Synthesis runs on spessasynth_core (Apache-2.0), a pure JavaScript synthesizer with no WebAssembly, combined with a bundled General MIDI sound bank (GeneralUser GS, 261 instruments and 13 drum kits). Standard MIDI files (format 0 and 1) and RIFF-wrapped RMID files (.rmi) are both supported. Everything happens directly in the browser - your MIDI file is never uploaded, and after the first visit the conversion even works offline.
Honestly framed: the result sounds like the bundled sound bank, not necessarily like the synthesizer or DAW the piece was originally composed with. WAV is lossless but noticeably larger than MP3 or OGG for longer pieces - both are available as space-saving alternatives.
| Input formats | MID, MIDI, RMI |
|---|---|
| Output formats | MP3, WAV, OGG |
| Batch processing | No |
| Processing | Locally in your browser (JavaScript) |
| File upload | None |
Limitations: Output sounds like the bundled General MIDI sound bank (GeneralUser GS), not the original synthesizer or DAW the piece was made with. A SoundFont embedded in an RMID file is not used. Lyrics from a karaoke MIDI (.kar) are not exported, only the audio. Very long or extremely dense files can render more slowly on weaker devices; a device-dependent duration cap guards against memory problems.
No. The whole synthesis runs locally in your browser - the file never leaves your device.
Not necessarily. The tool uses a bundled General MIDI sound bank (GeneralUser GS) - the sound depends on that bank, not on the synthesizer the piece was originally composed with.
All 128 General MIDI instruments (261 presets via variants) plus 13 drum kits - the full General MIDI standard.
Not yet - every file is rendered with the bundled General MIDI sound bank, even if an RMID file carries its own embedded SoundFont.
The limit depends on your device (desktop allows noticeably more than a phone) - very long or extremely dense pieces can slow the synthesis down.
A MIDI file only stores instructions, not audio data - the output is real rendered audio, so it is always noticeably bigger, regardless of the chosen format.
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