Contrast is one of the most potent arranging devices available. That doesn't always mean playing louder or busier or with more effects. It can mean playing simpler, more legato, making simple tone adjustments, etc. It can be quite effective to switch from dense and busy staccato parts to sparse & legato during solos, etc. If you do listen to the great trios, I think you'll notice that they often lock into a simpler (but still powerful) groove during solos. Intuitively, players usually want to play harder, faster, louder to create contrast, but that's only one of many options.