I would tend to go with the key of the song you're playing. The scales generally "hang out" in the key of the song, and passing (or grace) notes sort of tie 'em all together. Many songs shift modes and your scales and patterns shift right along with 'em... If you get lost, just work your way back to the tonic... It will help to know the song well, and you've got to be listening to both the group, and yourself simultaniously... Oh, and you definitely must have fun! ;^) ttr