Let’s turn the idea of playing outside on its head. Sometimes I’ll improv on a steady set of changes and let the band shift and crabwalk behind me. Some pieces are written this way, for example “Cape Verdean Blues”–you don’t have to constantly shift your scale a half step and back. It’s just an effect. On the A section of “When Lights Are Low”, you can stay on the Eb scale the whole time. It puts some tension in the latter part and resolves it at the cadence.
It helps me understand the larger structure of a song (in terms of chord changes) by thinking of the melody/solo and the rhythm section as two threads. They can be braided, they can be parallel, they can be knotted, they can be perpendicular on a loom, they can be unrelated. Most interestingly, they can be in motion or not.
Put more bluntly, if the piano and bass want to move to an A chord, I don’t have to–I’m the trumpet, dammit. I mean, y’know, maybe I *want* to… but I don’t *have* to.
Cape Verdean–Horace Silver: http://www.youtube.com/watch?v=0gt7QXwYpZo&feature=related
Try Miles for When Lights Are Low.