An American bass player, best known for his work as an original member of Blood, Sweat & Tears.

Born in Texas, Fielder started playing guitar at the age of 7, but also took up the upright acoustic bass in high school in Anaheim, California when he was about 17, influenced by jazz bass players such as Charles Mingus and Ron Carter. While at high school, he also became friends with Tim Buckley. Along with Buckley's friend Larry Beckett on drums, the three formed two bands: the Bohemians and the more acoustic Harlequin 3.

He began attending amateur night at the Troubadour in Los Angeles where groups like Buffalo Springfield and Mastin &  Brewer were playing. He switched to a Fender electric bass and played on Buckley's first two albums.

He also played with Mastin & Brewer with Mike Brewer and Billy Mundi after Mastin did not show up for a gig one time at the Whiskey A Go Go. Mundi knew Frank Zappa and recommended Fielder to join the Mothers of Invention. Although Fielder really wanted to specialise in bass by this time, Roy Estrada was already playing bass and so Fielder played rhythm guitar on Absolutely Free. However, by the time of the album's release, Fielder had successfully auditioned for Buffalo Springfield and Zappa omitted his credits from the sleeve.

Fielder had got to know Al Kooper and Bobby Colomby and played at Kooper's 1967 fundraising concert. Kooper, Colomby, Steve Katz and Fielder then did a few shows as a quartet at the Café Au Go Go. Fred Lipsius joined two months later and they played a couple of venues as a quintet, including the Fillmore East in New York.  Lipsius then recruited New York jazz horn players he knew and the final Blood, Sweat & Tears lineup debuted late November 1967 at The Scene in New York.

Fielder left BS&T in 1974 after 7 years, since when he has worked extensively as a session musician as well as being a standing member of Neil Sedaka's band since 1976. Credits include Chris Hillman's Slippin' Away (1976).