A flexible and consistently swinging drummer, who loved to drive a big band. As leader of the Juggernaut (a group he co-led with Nat Pierce starting in 1975, until the pianist's death in 1992), he got to push and inspire some of Los Angeles' best.

Capp found his initial fame playing with Stan Kenton's Orchestra (1951). Two years later, he settled in Los Angeles and became a busy studio musician. He played with everyone, including Ella Fitzgerald, Harry James, Stan Getz, Art Pepper and Benny Goodman.

Capp worked steadily on television shows and in the film studios in the 1960s and in the 1970s recorded extensively in a variety of settings for Concord. The Capp-Pierce Juggernaut (later known simply as the Juggernaut) sometimes sounded identical to the 1970s Count Basie Orchestra, and served as a perfect format for the drummer's colourful playing.

Capp was also a member of the Abnuceals Emuukha Electric Symphony Orchestra around 1967 when Frank Zappa recorded the orchestral parts for Lumpy Gravy.