Convert MIDI files to MP3 or WAV with real instrument sounds
A MIDI file is a list of notes, not a recording, so most phones, video editors, messaging apps and music sites cannot play it. This MIDI to MP3 converter plays the file through a SoundFont synthesiser in your browser and saves what it hears as an ordinary audio file — MP3 for sharing, or lossless WAV and FLAC for editing in a DAW or a video project.
The default sound set is FluidR3 Mono, a General MIDI SoundFont with all 128 instruments and a drum kit, so pianos, strings, guitars and drums come out as real sampled instruments. Load your own .sf2 or .sf3 to convert MIDI to MP3 with a SoundFont you already like. Before converting you can slow the piece down or speed it up, transpose it, mute parts you do not want, and listen to the result on the falling-note keyboard.
How to use the MIDI to MP3 Converter
- Drop a .mid, .midi, .kar or .rmi file on the box. Its length, tempo, notes and channels appear; “Ode to Joy” is loaded so you can try the page at once.
- Optional: press Use your own SoundFont to choose an .sf2, .sf3 or .dls file; otherwise the General MIDI set (14.6 MB, downloaded once) is used.
- Optional: set Tempo and Transpose, untick channels you want left out, and press Play to preview.
- Under Convert to an audio file, pick MP3, WAV, FLAC, M4A or OGG, the quality and the sample rate.
- Press Convert. The song is rendered faster than real time and encoded; listen to it in the player, then press Download.
MIDI to MP3 Converter features
Real SoundFont rendering
Every channel is played by a full SoundFont 2 synthesiser with envelopes, filters, reverb and chorus — the same engine as the MIDI Player.
Your own SF2 or SF3
Convert with any SoundFont or DLS bank on your computer, from a small piano font to a large orchestral set.
MP3, WAV, FLAC, M4A, OGG
MP3 up to 320 kbps, 16- or 24-bit WAV, 32-bit float WAV, FLAC, AAC in M4A and Ogg Vorbis, at 44.1 or 48 kHz.
Tempo, key and mutes
The tempo, transpose and channel choices you hear in the preview are exactly what is rendered.
Clean levels
The loudest peak can be normalised to −1 dB; otherwise the level is only lowered when it would clip. Silence after the last note is trimmed.
Private
Nothing is uploaded. The synthesiser, sound set and encoders run in your browser.
Which format to choose
For high-quality MIDI to MP3, the sound set matters far more than the bitrate: a detailed SoundFont at 192 kbps sounds better than a basic one at 320 kbps. FluidR3 Mono stores its samples in mono to stay small, so stereo width comes from panning, reverb and chorus. Choose 48 kHz when the audio is going into a video, 44.1 kHz for music.
| Format | Quality setting | Best for |
|---|---|---|
| MP3 | 256 kbps by default; 320 kbps is the maximum | Sharing, phones, messaging apps, uploads |
| WAV | 16-bit, 24-bit or 32-bit float PCM | Editing in a DAW or video editor; no quality loss |
| FLAC | 16- or 24-bit, lossless | Archiving at about half the size of WAV |
| M4A (AAC) | 96–192 kbps | iPhone, Mac and car players |
| OGG (Vorbis) | Quality 3–9 | Games and Android |
How the conversion works
The file is read by the open-source spessasynth_core synthesiser (Apache-2.0), which follows every note, program change, controller and tempo change on all 16 channels (more in multi-port files). Instead of playing to your speakers it hands back blocks of samples, about half a second at a time, until the song and three seconds of reverb tail have been rendered. Trailing silence is trimmed and a 10 ms fade is added so the file does not end with a click.
Resampling and encoding use the same code as this site’s other audio tools: MP3 is encoded with LAME through Mediabunny’s encoder extension, M4A uses your browser’s AAC encoder when it has one, and WAV is written directly with dither for 16-bit output.
Good to know
- A MIDI file sounds different on every synthesiser. If you want the sound of a particular program or keyboard, load that SoundFont.
- General MIDI program numbers and drum notes are honoured; GS and XG bank selects are used when the SoundFont has those banks.
- Karaoke .kar files convert normally, but their lyrics are not written into the audio file.
- Songs up to 20 minutes at the chosen tempo can be rendered; long WAV files need a lot of memory on phones.
MIDI to MP3 Converter FAQ
How do I convert MIDI to MP3 for free?
Drop the .mid file on this page, keep MP3 selected and press Convert to MP3. The first conversion downloads the 14.6 MB General MIDI sound set; when the file is ready, press Download.
How do I convert MIDI to MP3 with a SoundFont?
Press Use your own SoundFont, choose your .sf2 or .sf3 file, check it with Play, then convert. The file stays on your computer.
Can I convert MIDI to WAV?
Yes. Choose WAV (lossless) under Format. 16-bit is CD quality; 24-bit and 32-bit float suit further mixing.
Why does my converted MIDI sound different from my keyboard or game?
MIDI stores notes, not sound. Each device uses its own instruments, so the result depends on the SoundFont. Load the one your keyboard or game uses to get closer.
Can I change the tempo or key before converting?
Yes. Tempo (25–200 %) and Transpose (±12 semitones) are applied to the render, and unticked channels are left out.
Is there a file size or length limit?
MIDI files up to 32 MB and songs up to 20 minutes at the chosen tempo. Nothing is uploaded, so there is no queue.
Can I turn an MP3 back into MIDI?
That is a different job — note transcription. Use the Audio to MIDI converter, which works best on solo instruments.