Stewart's early career also included notable work as a voice actor. He provided the narration for "Scenes in the City", a long jazz composition with a text by Lonne Elder and Langston Hughes that appeared on Charles Mingus' 1957 album A Modern Jazz Symposium of Music and Poetry. In 1961, Stewart recorded an album of Langston Hughes' poetry on Folkways Records: "Langston Hughes' The Best of Simple". He was also a member of the San Francisco-based improv group, "The Committee" and appeared in 1969 on "The Dick Cavett Show".