Drop in a .mid file and hear it as audio. We render it with a sampled General MIDI sound set, then hand you the MP3 — along with each part as its own track, slow practice versions, and a score that highlights the notes as they play.
A MIDI file holds no sound at all. It is a list of instructions — note on, note off, which instrument, how hard — which is why a 40 KB .mid can carry a five-minute orchestral piece. Playing it means handing those instructions to something that can make noise, and the result depends entirely on what that something is. The same file sounds like a cheap 90s keyboard through one synthesizer and like a concert grand through another.
We render with FluidR3, a sampled General MIDI sound set — real recorded instruments rather than synthesized tones. It will not pass for a studio recording of a live band, and no MIDI renderer will: expression, phrasing and room sound are not in the file to begin with. For rehearsal tracks, backing parts, and hearing an arrangement before anyone plays it, it is more than good enough.
Because the parts are separate in the file, they can stay separate in the output. Alongside the full mix you get one MP3 per instrument or voice, so a choir member can practise against their own line, or a bassist can mute the bass and play along with everything else.
The rehearsal view adds the two things a plain audio file cannot do: slow the playback to 50-90% without dropping the pitch, and loop a difficult bar until it sticks. The notation scrolls and highlights in time with the sound, so you always know where you are.