Scott, I do the same as often as I can. Luckily, I have a pool of great players who do unbelievably well with minimal/no rehearsal.
I'm particularly fond of adding a horn or two
or a great guitar. I'm talking about "any tune...any key" folks.
Makes things interesting, challenging and fun, almost like the jam sessions for years gone by.
Russ
[This message has been edited by captain Russ (edited 08-14-2006).]