Midi only contains the note information not the sound waves or 'Patches', one reason it is so small compared to other formats. The quality of the midi file being rendered often depends on the quality of the patch bank installed on the playback device. There is a standard patch set called General Midi (GM) which is often used - Windows has one built in - but many musicians use midi and just associate the note data with sampled sfx or other sounds on their synth.
Closest formats you'll get to this, ie. formats that don't contain patch data, are stuff from old consoles, like SID, AHX, YM that often had custom trackers, or more recently that Farbrauch synth that Rbz has been posting library bindings for.
Jim
