Tension and release in a solo over a vamp
The easiest and most effective device that you have at your disposal when soloing over a vamp is choosing when to play with the band and when to play something against what the band is playing. This may sound like an oversimplification, but this is basically how the tension and release work in this kind of a solo. Essentially, playing against what the band is doing produces tension that is released when you finally play something in unison.
In the clip above notice how I would periodically release in this fashion by playing the hits of the vamp with the band. In my experience, doing this occasionally helps keep the band together as well as the audience engaged in the music.
|He is actually this cool.|
To practice this, try something straightforward like improvising a vamp, and then trying to sing it while you play against/with it. You will quickly discover that this seemingly simple exercise is actual fraught with difficulty, and is something you really need to work at to develop.
The other thing I would recommend you do is to listen to some great players soloing over a vamp. One of the drummers I always love to listen to and draw from for this type of playing is Roy Haynes. Check him out here with his band: