Percy Heath, 56, was the bassist who provided the throb of the Modern Jazz Quartet, and brother Jimmy, 52, is a saxophonist and flutist who used to be known as "Little Bird" and led one of the first groups to showcase John Coltrane. (Drummer Albert is no longer with the brother act.) In Motion is full of fluid, cohesive jazz, contemporary but with a touch of bebop traditionalism and nary a hint of electronic fusion. Permanent sidemen Keith Cope-land (drums), Stanley Cowell (piano) and Tony Purrone (guitar), relative youngsters all, contribute some contemporary sketches but the Heaths, while they're a kind of living legacy, hardly need rejuvenation. Theirs is a jazz that's always modern.