Here is a favorite of mine from when I was younger. Here is the order of solos on Bela Fleck's driving bluegrass roadhouse, "Whitewater."
Bela Fleck -- Melody of the tune
Sam Bush -- Mando solo highly based on the melody
Tony Rice -- What the heck?!?
Bela Fleck -- re-establishes the melody with a couple twists
Jerry Douglas -- a very melody-based solo, gets a little looser towards the end
Stuart Duncan -- creates a new melody on the fiddle in the A section, before playing a syncopated series of double stops over the B section
Bela Fleck -- finishes with the melody, then Sam, Jerry, and Stuart join in doubling the B section.
Here's my question: Why does Tony's solo work?
Tony's solo is bluesy, driving and rhythmic. There is no melody of the song in it at all. He does use a couple techniques though, starting with long bluesy single-note runs at the front end of the solo, and later juxtaposing that with series of syncopated double and triple stops. He starts low, then goes higher. It has a quiet intensity to it. Mostly though, its expertly-placed blues licks.
My feeling, is that Tony's solo works because its the opposite of Bela and Sam's. Bela establishes a clear melody, Sam backs it up, and by the time Tony plays, the listener is ready for something a little different. Then Bela comes back in, and reclaims the melody of the song. I wonder if Tony had stuck closer to the melody, would Bela have instinctively stepped farther out on his second solo? To those who say Tony never sticks to the melody, listen to his Church Street Blues album. There, he plays solo, and has to play the melody, because he's the only one there to do it.