I think that far too many people see "MIDI" and bring preconceptions to the thing based on their own experiences, which, apparently, aren't all that deep.

If you've recently been to the movie theater, chances are very good that you heard MIDI instruments in the Soundtrack or Underscore, emulating orchestras and quite a few other sounds.

A MIDI track can be recorded just as any audio track can.

If you are playing a good sounding and good reacting MIDI instrument, that performance can be captured exactly.

With certain Patches, such as Piano, with a good MIDI synth, it can be difficult to impossible to listen to the resulting recorded track and tell it apart from a well-recorded MIDI piano performance.

The MIDI SuperTracks are live performance MIDI recordings that are handled in much the same fashion as the Audio based RealTracks are. Phrases, not single notes, intelligently incorporated into your chord changes.

--Mac