rikki:
Sorry -- I misspoke. What I usually do is take MIDI files (such as George Shearing or anyone) and then mute certain tracks in BIAB (melody, for instance, solo sometimes, sometimes piano, etc.). Then I play along with my piano VST. Since MP3 to MIDI conversion is such a bloody pain, I rarely even try it. But there are SO many MIDI files available, and so many sound really fine in BIAB.
(Last evening I was playing the lead on "Mas Que Nada" -- if you know that tune): in BIAB; slowed down a bit for my cold fingers; piano comping on but I soloed melody in an electric piano mode -- worked nicely. Then I left all parts on but the piano and comped as well as I could read the notation. As I said before, this for me is very necessary practice.