As everyone knows, MIDI is not sound, but instructions for playback of sound. The actual sound is generated by the local synth (which makes MIDI a good choice for internet music). If you burn a MIDI file to CD, it's just data and can't be played on a CD player. You have to send the playback to a synth, record the synth in a digital editor and burn those files to create actual music files.
But create a playlist in iTunes with MIDI files, then burn that to CD and it burns audio files that can be played back on a CD player. I'm guessing it converts the QuickTime synth sounds in real time while burning. Not even ProTools has a similar feature. Pretty slick.

