Bill,

Each Midi kit normally has a limited number of snares (regular, gated, piccolo etc.), toms, cymbals etc.

In an Audio style many different snares, for example, can be played either at the same time, or even overdubbed to provide several variations of the same snare. Or, similar snares each might be struck at a different point on the drum head, providing many varied tones.

You can also have a drummer (with or without long arms ) and a percussionist, or, as in some of the more exotic audio styles, several drummers/percussionists, playing at the same time.

Usually, with MIDI drums the "feel" is not going to be as realistic as with a drummer and a percussionist actually playing and recording different beats, fills and passages.

Because Yamaha uses the very expressive Mega Voices (and now, SA/SA2) for the style's bass and guitars (and other instruments), it was deemed only necessary to use Audio only for the drums/percussion tracks...tracks that would benefit from Audio instead of Midi.

I think they have made the right decision.

I hope this helps...it's the best I can do.

Ian