no, seriously! I suppose i might be asking for trouble by asking this but does anyone use this? The hal leonard edition of the Classical fake Book. I suppose i can see some value in it in having 600 or so themes, melodies etc. to refer to; might be better for someone playing violin, but i wonder if anyone uses this to actually play a piece and would that be something someone would do in a casual setting? It just seems somewhat heresy almost to play a classical piece and improvise the bass part and almost something I wonder if you'd even want to start doing...or would you? Might there even be some value in improvising this way or would you end up just sounding like the ultimate elevator musician?

If your improvisations sound like elevator music, then improvising on classical themes will still sound like elevator music. If otherwise, then it will sound like whatever your style sounds like.

A lot of classical pieces have catchy melodies. If you like to improvise on a catchy melody, it doesn't seem like it makes any difference whether it's Liszt, Grieg, or Elton John. It's not playing the classical repertory, but it's certainly not heresy to me.