Matthews started his career as the bandleader for James Brown. Following that, for many years, Matthews worked steadily as a free-lance arranger and writer on albums, singles, radio and TV commercials and film scores. He's arranged or composed albums or tracks for Buddy Rich, Bonnie Raitt, T-Bone Walker, Blue Mitchell, Mark Murphy, the J.B.'s, Starland Vocal Band, Stephanie Mills, Earl Klugh, Phoebe Snow, Donald Bird, Crystal Gayle, David Sanborn, Billy Joel, Paul Simon Frank Sinatra and Paul McCartney. In 1975 he won a Grammy for record of the year, for arranging work on Paul Simon's album "Still Crazy After All These Years" as well as a Clio for his work for 3M.

From 1975 - 78 David was the staff arranger for CTI Records composing, arranging and producing records for stars such as Nina Simone, Hank Crawford, Art Farmer, Joe Farrell, Ron Carter, Idris Muhammad, Jim Hall, Grover Washington, Jr. and George Benson.

Matthews composed the scores for The Fight featuring Mohammad Ali and Joe Frazier and Bedtime Eyes in which he also performed with his group, the Manhattan Jazz Quintet, which has been one of Japan's top jazz groups since 1984. He orchestrated film scores for Parallax View, The Stepford Wives, Night Moves, and Washington D.C., A City Out of Wilderness.

Matthews arranged the Simon and Garfunkel Reunion Concert in Central Park, the Memorial Concert for John Lennon by the Cincinnati Pops Orchestra, Julian Lennon's debut Album, "Valotte," Robert Plant's "The Honeydrippers, Volume I," Paul McCartney's "Angry," Frank Sinatra's, "L.A. is My Lady," and Billy Joel's "An Innocent Man" followed by Billy's hit singles Easy Money and Second Wind. He was also happy to arrange Why Should I Worry for Walt Disney Studio's animated film Oliver.

In recent years there has been a resurgence of interest in Matthew's music, both from his James Brown period and the music he wrote in the 1970's. Many hip-hop artists such as The Notorious B.I.G., Nas, Methodman and Redman, and The Large Professor have sampled some of that music. The track Sandworms, from his album "Dune," has been sampled numerous times, and that album "Dune" is in the Hip Hop Hall of Fame. His very first album, "The Grodeck Whipperjenny," recorded for James Brown Productions in 1970, has achieved cult status and original vinyl pressings are currently selling for $200 apiece. And his composition/production of "Mr. Hot Pants a.k.a. Across The Tracks" by The Believers has been rated the number-one 45" single of the genre Deep Funk.