Q: whats a good way to improvise on a C7 | Bb7 vamp? i experimented with the Bb major pentatonic because it would basically work on both chords. going from one mixolydian scale to the other sounded very obvious... how can i play a cool line wirhout implementing  the harmonic movement so strong?
A: just play in C mixo, no 6, and see what develops. see what concessions you need to make on that second chord. hint, Ab's will be more available on the second chord. or a better strategy is just make every note available all the time and if you play it for long enough you should handily learn which ones not to play when