(The comment starts at the 12:04 mark, clicking “play” should automatically take you there)
What it sounds to me is like they have a suite of music, probably a handful of cues mixed into a larger one, that has a combined track total of 4,000 tracks. So it’s likely that 4,000 tracks aren’t playing back at once, but just that when you combine all of the tracks from the individual cues, which may be anywhere from 40-250 per cue, you have a total of the amount Alan said. So, for the sake of argument, there isn’t one track for the piano in the entire suite, but instead multiple tracks for piano, but each of the individual tracks for the piano correspond to only a single cue.
Bottom line… it looks like The Dark Knight Rises will have the biggest music mix of all time!
Thanks Alexander for the heads up!