Thanks, Brian.

It's not a question of whether someone is really playing it originally at some tempo and key, printed right down to an audio file.

The questions are: to what extent the front end of the compiling for any given song uses midi to tell the ... for lack of better language ... the RealTracks 'engine' what part of the audio to select, time stretch and pitch shift to come up with the RealTrack? (Samplers triggering real audio to midi messages are nothing new. I'm sure the RealTracks 'engine' is built upon that concept.)

The other question would be (and thanks again for your above helpful amplification and direction!) how the chart comes out 'right' after you have selected a key, tempo and progressions? I think obviously, there must be ongoing compiling of an underlying data set ... otherwise there would be no way for the program to show you the data synced to your song creation.

Prado