Tom Harrell was born in Urbana, Illinois, United States, but moved to the San Francisco Bay Area at the age of five. He started playing trumpet at eight, and within five years he was playing gigs with local bands. In 1969 he graduated from Stanford University with a music composition degree and joined Stan Kenton's orchestra, touring and recording with them throughout 1969. Harrell pursued his musical career despite experiencing symptoms of schizophrenia since he was an adolescent.
After leaving Kenton, Harrell played with Woody Herman's big band (1970–1971), Azteca (1972), the Horace Silver Quintet (1973–1977), with whom he made five albums, the Sam Jones-Tom Harrell Big Band, the Lee Konitz Nonet (1979–1981), George Russell, and the Mel Lewis Orchestra (1981). From 1983 to 1989, he was a pivotal member of the Phil Woods Quintet and made seven albums with the group.
In addition, he performed with Vince Guaraldi on the Peanuts television specials You're Not Elected, Charlie Brown (1972), There's No Time for Love, Charlie Brown, A Charlie Brown Thanksgiving (both 1973) and It's a Mystery, Charlie Brown (1974).
Harrell also performed with Bill Evans, Dizzy Gillespie, Jim Hall, Ronnie Cuber, Bob Brookmeyer, Lionel Hampton, Bob Berg, Cecil Payne, Bobby Shew, Philip Catherine, Ivan Paduart [fr], Joe Lovano, Charlie Haden's Liberation Orchestra, Charles McPherson, David Sánchez, Sheila Jordan, Jane Monheit, the King's Singers and Kathleen Battle among others. Harrell is featured on Bill Evans' final studio recording, We Will Meet Again, which won a Grammy Award for Best Instrumental Jazz Performance, Group.
While Harrell recorded several albums as a leader during his tenure with the Phil Woods Quintet, it was after his departure that he started producing albums as a leader, in succession for Contemporary Records (now owned by Concord), Chesky, and RCA/BMG. During his years as a BMG artist (1996–2003) first with RCA, then Bluebird and finally Arista, Harrell made six albums, many of which feature his arrangements for larger groups. Since the early 1990s, Harrell has toured and performed with his own groups of various sizes and instrumentation.
Harrell is a prolific arranger and composer. He has arranged for Vince Guaraldi's work on Peanuts, Carlos Santana, the Metropole Orchestra, the Danish Radio Big Band, the Vanguard Jazz Orchestra, and Elisabeth Kontomanou with the Orchestre National de Lorraine [fr], among others. His compositions have been recorded by other jazz artists including Ron Carter, Kenny Barron, Art Farmer, Chris Potter, Tom Scott, Steve Kuhn, Kenny Werner and Hank Jones. Harrell's composition and big band arrangement entitled "Humility" was recorded on the Grammy-winning album by Arturo O'Farrill's Afro-Latin Jazz Orchestra, Song for Chico. As a composer and arranger, Harrell works in different genres, including classical music.
