This guy is actually a friend of mine.  We played trumpet together in a Broadway show called Blast! in the early 2000's.  He has gone on to become quite well known and for good reason,  he's kinda BA.  Anyway, here is an article that he posted on http://www.21stcenturybrass.com/multi-tracking/.  This article and video are about using recording tools as a practice aids.  Very cool.  I remember him trying this in his apartment in 2001 with a silent brass mute.  Looks like he figured it out!