MF sat in with the Letterman band at least twice---that they didn't let him play a feature during broadcast either time is a shame, but if he had fun, good enough I guess.

PURE RUMOR: I hate spreading rumors, but here I am doing it. We know that Doc and MF had a lot of respect for each other. The rumor is that Carson heard somehow that MF made joking references in his clinics about "5 minute heroes" who can force out decent high-note playing for 5 minutes and then are shot. Carson thought MF was knocking Doc. He wasn't of course.

There are a lot of problems with that rumor in so many ways, but there it is.

The point is, it shows a lot of MF fans and others have wondered why MF wasn't on the Tonight Show in some capacity at some point, especially 1974-1983 when his pop fame was at its zenith.