Free online
MIDI to MP3 Converter
Turn a MIDI file into audio that sounds the way you want. A real SoundFont synthesiser renders every part of the file on its own instrument — swap them, mute them, load your own SoundFont, change the tempo or key, and hear it before you download the MP3, WAV or Ogg. Nothing is uploaded.
- 128General MIDI instruments, plus drum kits
- MP3, WAV or Ogg — hear it before you render
- Runs in your browser — nothing uploaded
Drop a MIDI file here
or choose a file
.mid, .midi, .kar and .rmi — any size, any number of tracks
Your file never leaves this browser. Nothing is uploaded.
GeneralUser GS, 8 MB, fetched once and cached by your browser.
The preview and the rendered file use the same synthesiser and the same settings.
This runs faster than real time. A three-minute file usually takes well under a minute.
- Nothing is uploaded The synthesiser runs on your own machine. Your MIDI file never touches a server.
- No size or length limit A four-bar loop or a forty-minute symphony. There is no cap and no queue.
- Free, no account No signup, no credits, no watermark, no trial. Render as many files as you like.
The sound is yours to choose
A real SoundFont synthesiser, every part of the file on its own instrument, and a play button before the render button.
Every part on its own instrument — and you can change any of them
A MIDI file names an instrument for each of its parts, and most online converters throw that away and play the whole thing on one generic patch. This one reads the file the way a synthesiser does: the piano part on a piano, the bass on a bass, the drums on a drum kit. The table under the file lists each part with the sound it asked for, and any of them can be swapped for one of the 128 General MIDI instruments or muted. Want the melody on a cello instead of a flute, or the strings without the drums? Change it, press play, and hear it before you render.
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A real SoundFont, or bring your own
Rendering uses GeneralUser GS, a complete General MIDI bank with 274 instruments and 13 drum kits, built by S. Christian Collins and refined for over twenty years. If you have a SoundFont you prefer — a concert grand, an orchestral library, a vintage synth collection — load the .sf2, .sf3 or .dls and the file renders with it instead. The bank is read in your browser; it is not uploaded either.
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Hear it first
The preview and the rendered file come from the same synthesiser with the same settings, so what you hear when you press play is exactly what you get when you press render. No more converting, downloading, listening and converting again.
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MP3, WAV or Ogg Vorbis
MP3 at 128, 192 or 320 kbit/s for anything that has to play anywhere; 16-bit WAV for a lossless master to bring into a DAW or burn to CD; Ogg Vorbis for a small file in an open format. 44.1 or 48 kHz. All three are encoded with the reference encoders, LAME and libvorbis, compiled to run in your browser.
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Tempo and key
Slow a piece down to half speed for practice or push it up for a backing track — the whole file re-times, tempo changes and all. Transpose up to an octave either way for a singer; drum parts are left where they are so the kit does not change.
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Faster than real time
The old version of this tool played the file in real time and recorded it, so a four-minute file took four minutes and a background tab could drop notes. This one renders offline in a Worker thread, several times faster than real time. A typical song is done in well under a minute, and switching tabs cannot harm it.
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Reverb and chorus, as written
MIDI files carry reverb and chorus levels per part. They are honoured, and can be switched off for a dry mix if you plan to add your own effects afterwards.
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Format 0, Format 1, karaoke and RMID
Single-track and multi-track standard MIDI files, .kar karaoke files and .rmi files with an embedded SoundFont are all read. Files up to sixteen channels, with program changes, pitch bends, sustain and expression controllers, all rendered.
From MIDI to audio in three steps
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Drop in your MIDI file
Drag a .mid, .midi, .kar or .rmi onto the panel or pick one. The parts, instruments, tempo and length appear immediately. The synthesiser and its 8 MB sound bank load in the background the first time; your browser keeps them for next time.
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Choose how it sounds
Leave every part as the file wrote it, or swap instruments, mute parts, load your own SoundFont, and set the tempo and key. Press play at any point — the preview is the render.
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Render and download
Pick MP3, WAV or Ogg and a bitrate, and render. The file is ready in well under a minute for a typical song, with a player to check it and a download button. Then play it back, or turn it into a video.
Looking for something different?
This tool turns a MIDI file into a sound recording. If you are starting from a recording, or you want to read the music rather than hear it, start somewhere else.
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You have audio and want MIDI
Transcribe an MP3, WAV or video into a MIDI file, any instrument, chords included.
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You want to read or play it, not export it
Play the file with the same instruments, or turn it into sheet music you can print.
How the rendering engine works
SpessaSynth and the GeneralUser GS bank, running on your own machine.
The synthesiser
SpessaSynth, an open-source SoundFont 2 / SF3 / DLS synthesiser written in TypeScript and released under the Apache 2.0 licence. It implements the SoundFont specification the way a hardware sampler does — sixteen channels, sample-based voices with ADSR envelopes, low-pass filters, LFOs and modulators — and understands the General MIDI, GS and XG extensions that real-world MIDI files use for drum kits and bank selects.
- Engine
- SpessaSynth (spessasynth_lib 4.3)
- Sound bank
- GeneralUser GS 2.0.3 — 274 instruments, 13 drum kits, 920 samples
- Bank download
- 8.4 MB (SF3, Vorbis-compressed), fetched once
- Channels
- 16 per port, multi-port files supported
- Polyphony
- Up to 350 simultaneous voices
Where it runs
Everything happens in this tab. The synthesiser runs in a Web Worker so it never blocks the page, and feeds a small AudioWorklet for the live preview. Rendering does not go through the audio output at all: the Worker synthesises the whole file to a stereo buffer at the sample rate you chose, which is why a long file renders several times faster than real time and why switching tabs cannot damage it. No part of the MIDI file, or of a SoundFont you load, is transmitted anywhere.
Encoding
The rendered buffer is peak-normalised so a sparse solo and a dense arrangement come out at a sensible level, then encoded in a second Worker.
- MP3
- LAME, constant bitrate 128 / 192 / 320 kbit/s, joint stereo
- WAV
- 16-bit PCM, stereo, uncompressed
- Ogg
- libvorbis, quality 6 (about 192 kbit/s)
- Sample rate
- 44.1 kHz or 48 kHz
What the settings change
- Instrument swaps lock a program on that channel, so the file's own program changes cannot override your choice mid-song.
- Tempo rewrites every tempo event in the file by the same factor before it reaches the synthesiser, so preview and render agree exactly.
- Transpose shifts each pitched channel by whole semitones; the drum channel is excluded because on a drum kit each key is a different sound.
- Reverb and chorus are the synthesiser's send effects, driven by controllers 91 and 93 in the file. Off means a completely dry render.
- A SoundFont you load takes priority over the built-in bank; any preset it lacks falls back to GeneralUser GS.
Good to know
- The sound bank is cached by your browser after the first load, so later visits start immediately.
- Files that rely on a specific commercial sound module (Roland SC-88 variations, XG-only voices) will render with the closest General MIDI equivalent.
- Very dense files at 320 kbit/s and 48 kHz take longest to encode; the render itself is rarely the slow part.
- Safari supports everything used here from version 14.1; Chrome, Edge and Firefox from their current releases.
Frequently asked
How do I convert MIDI to MP3 for free?
Three steps, none of which need an account:
- Drop your .mid or .midi file onto the panel above.
- Check the instruments in the table, swap or mute any you want, and press play to hear it.
- Choose MP3 (or WAV or Ogg), press render, and download the file when it is done — well under a minute for a typical song.
Why does my MIDI file sound different in every player?
Because a MIDI file contains no sound. It is a list of instructions — play this note, on this instrument number, at this time — and whatever plays it back supplies the actual sounds from a sound bank. Windows' built-in synthesiser, a phone, a DAW and a keyboard all have different banks, so the same file sounds different on each. When you render to MP3 you freeze one particular rendering, which is why the choice of sound bank and instruments matters more here than in any other kind of audio conversion.
What is a SoundFont, and which one does this use?
A SoundFont (.sf2, or the compressed .sf3) is a bank of recorded instrument samples plus the rules for playing them — the thing that turns MIDI instructions into sound. This tool ships with GeneralUser GS, a complete General MIDI bank of 274 instruments and 13 drum kits by S. Christian Collins, widely regarded as the best free GM bank of its size. You can also load your own SoundFont or DLS file and render with that instead.
Can I change the instruments before converting?
Yes. Every part of the file is listed with the instrument it asks for, and each can be swapped for any of the 128 General MIDI instruments — piano to harpsichord, flute to cello, strings to choir — or muted. Drum parts stay on a drum kit. Press play to check the result before rendering.
Is MIDI to MP3 conversion done with AI?
No, and it does not need to be. A MIDI file already says exactly which notes to play; the only job is to play them with good sounds, which a sample-based synthesiser does deterministically. AI is useful in the other direction — turning a recording back into notes — which is what our MP3 to MIDI converter does.
Will my MIDI file's instruments be preserved?
Yes. The file's program changes are read per channel, including bank selects for GS and XG files, and each part is rendered with the instrument it names — not with one sound applied to everything. If a file asks for a voice the bank does not have, the nearest General MIDI equivalent is used.
Can I convert MIDI to WAV instead of MP3?
Yes. Choose WAV for a 16-bit, uncompressed stereo file at 44.1 or 48 kHz — the right choice if you plan to edit, master or burn it. Ogg Vorbis is also available for a small file in an open format.
Is there a file size or length limit?
No. Because rendering happens on your own machine there is no upload to cap. A forty-minute MIDI file is fine; it just takes proportionally longer to render and the WAV will be large — around 10 MB per minute at 44.1 kHz.
Is my MIDI file uploaded anywhere?
No. The synthesiser, the sound bank and the encoders all run inside this browser tab. The only download is the sound bank itself, which your browser caches. Your file, and any SoundFont you load, never leave your device.
Can I slow the file down or change the key?
Yes. The tempo slider re-times the whole file from half speed to double speed, keeping any tempo changes it contains in proportion — useful for practice tracks. Transpose moves every pitched part up or down by up to twelve semitones, leaving the drums alone. Both apply to the preview and the render.
Does it handle multi-track MIDI files and drums?
Yes. Format 0 and Format 1 files, up to sixteen channels per port, are rendered together into one stereo mix with each track on its own instrument. Channel 10 is treated as drums in the General MIDI way, with the file's own kit selection honoured.
Why does the first conversion take a moment to start?
The sound bank is 8 MB and is fetched the first time you drop a file, while you are looking at the track table. After that your browser keeps it, so the next visit starts immediately. The render itself is several times faster than real time — well under a minute for a typical song.
How do I convert MP3 back to MIDI?
That is the harder direction — a recording has to be transcribed into notes. Our MP3 to MIDI converter does it with a neural network, in the browser, for any instrument.
Can I use the MP3 commercially?
The rendering is yours, subject to the rights in the MIDI file itself. GeneralUser GS is licensed for use in commercial music without restriction. If you load your own SoundFont, its licence applies.