Midy by nemal byt problem do MP3 dostat, uplne nejblbejsi zpusob by byl spustit prehravac a soucasne to nahrat do WAV a prevest na MP3.
Jinak na to existuji softy, jako napr.
http://www.snapfiles.com/screenshots/miditowav.htm
Tady mas stranky s nejakymi konvertory, ktere to prevedou primo z MIDI na MP3:
http://www.audioutilities.com/midi-wav-converter/m idi-wav-converter.htm
http://www.mp3towav.org/midi-to-mp3.asp