You can not include the actual sounds you used in the MIDI file. Wave files are sound - it tells you what it sounds like, but not how you should play it. MIDI tells what notes you should play, but not what it sounds like.
That gives you a wave/mp3 you can actually use. wav file, then save in Audacity as an mp3 or use another wave-to-mp3 converter (iTunes / Windows Media Player can both do this).
Plug your M50's audio outputs into your computer, use something like Audacity to record it as a.
