Ditmas began his musical career eighteen years old as a companion of Judy Garland. After that, he was for several years at the Gil Evans Orchestra, with whom he recorded until the mid- 1970s several albums as 1973 Svengali, 1974 The Gil Evans Orchestra Plays the Music of Jimi Hendrix or 1975 There Comes a Time. He also worked with Lee Konitz, David Sanborn, Michael and Randy Brecker, Steve Kuhn and Stan Getz. He also appeared in the Merv Griffin Show and worked with Barbra Streisand.
Later, he worked on recordings of Jaco Pastorius, Enrico Rava, Paul Bley and Jean -Luc Ponty. As a bandleader, he took the 1994 album What If with guitarist John Abercrombie, Paul Bley, bassist Dominic Richards and saxophonist Sam Rivers on.