At one time swing was just another kind of dance music with a rhythm of utilitarian regularity. It was only in the hands of drummers like Sid Catlett and Sonny Greer that swing acquired enough flexibility to be useful in jazz. Baltimore's Dennis Chambers, a drummer for Parliament-Funkadelic and John Scofield, is now bringing a similar flexibility to another dance music, funk. On Is What It Is, by former Miles Davis guitarist Mike Stern, Chambers proves that funk can be as infinitely variable as swing, and the soloists respond with a rhythmic freedom unusual in fusion. --Geoffrey Himes