He joined Jimmie Lunceford's band in 1933 and contributed many hit arrangements to the band, including "My Blue Heaven" and "Ain't She Sweet". In 1939, he became one of the first African Americans with a prominent role in a white band when he joined Tommy Dorsey as an arranger, though he stopped playing trumpet at that time. (Fletcher Henderson joined the Benny Goodman orchestra as the arranger in the same year.) He led the transition of the Dorsey band from Dixieland to modern big band. His joining was instrumental in Buddy Rich's decision to join Dorsey. His arrangement of "On the Sunny Side of the Street" was a big hit for Dorsey, as were his own compositions "Yes Indeed" (a gospel-jazz tune that was later recorded by Ray Charles), "Opus One," "The Minor is Muggin'," "T.D.'s Boogie Woogie," and "Well, Git It."