How to convert MIDI to audio
- Open a .mid file, or try the demo.
- Pick a sound set: the built-in General MIDI set, or your own SoundFont.
- Choose WAV or MP3, change the speed if you like, and leave out any channels you don't want.
- Press Render audio, listen, and download.
Rendering runs on your computer, usually many times faster than real time: a three-minute song takes a few seconds. Very long or very dense files take longer and need more memory.
What gets played
The renderer is a full SoundFont synthesizer (SpessaSynth) that follows the General MIDI standard. Program changes pick the instruments, channel 10 plays drums, and controllers like sustain, volume, pan, pitch bend, reverb and chorus all work. Files made for Roland GS or Yamaha XG modules play their extra drum kits and variation sounds too.
The built-in sounds are GeneralUser GS by S. Christian Collins, a compact, balanced General MIDI set, free to use for any music, commercial included.
Questions
Is my file uploaded anywhere?
No. The MIDI file, the sounds and the audio all stay in your browser. The only download is the sound set itself, once.
Why does a MIDI file need to be "rendered"?
A MIDI file holds no sound, only instructions: which note, when, how hard, on which instrument. To hear it, something has to play those instructions on instruments. This tool plays them on a sampled General MIDI sound set and records the result, faster than real time.
Which sounds does it use?
GeneralUser GS by S. Christian Collins: all 128 General MIDI instruments plus drum kits, in about 8 MB. You can also load your own SoundFont (.sf2 or .sf3) or DLS file, for example a bigger piano or an orchestral set. The file is read locally and never uploaded.
WAV or MP3?
WAV is lossless, the best choice for a DAW or for editing further; 24-bit keeps more headroom. MP3 is about a tenth of the size, good for sharing, email and phones. 192 kbps is hard to tell from the original; 320 kbps is the most MP3 allows.
Why does the audio start with silence?
If the MIDI file starts with an empty bar or a pickup, the audio keeps it, so it lines up with the MIDI when you drop both into a DAW.
What does "Normalize" do?
It turns the whole file up or down so the loudest moment peaks at −1 dB. Without it, busy arrangements can clip and quiet ones come out soft; the tool warns you if the audio clipped.
Can I export one instrument at a time (stems)?
Yes. Click the channels you don't want to leave them out, render, and repeat for each instrument. Every file has the same length and start, so they line up in a DAW.
Does it play pitch bends, sustain pedal and other controllers?
Yes: pitch bend, sustain, volume, pan, expression, modulation, reverb and chorus sends, RPNs and the common GS and XG messages, the same way a hardware General MIDI module would.