Adopted at birth by Hollywood talent agents, he grew up in Beverly Hills, California, and was babysat by Marilyn Monroe, who was represented by his father in the early stages of her career.
He also composed a symphonic piece, "Western Impressions," the first orchestral work by a student to be publicly performed by the school's orchestra (under the direction of Robert Holmes).
In 1967, he began working as a session musician, specializing in electric bass, with a litany of notable blues, folk, and rock performers, including Mike Bloomfield, Nick Gravenites, Mississippi Fred McDowell, John Lee Hooker, Brewer & Shipley (a longstanding collaboration that encompassed their 1971 Top Ten hit "One Toke Over the Line"), Tom Fogerty, Maria Muldaur (who was in a relationship with Kahn for several years in the 1970s), Al Kooper, Jackie DeShannon and Otis Rush.
In addition to serving as the band's nominal manager (these responsibilities were delegated to Grateful Dead employees Rock Scully and Steve Parish), he selected the group's repertoire in consultation with Garcia.
"[6] Despite underlying acrimony stemming from his relationship with Garcia, Kahn did occasional work for the Grateful Dead, serving as a recording engineer alongside Betty Cantor-Jackson and Bob Matthews for the band's aborted Egypt '78 live album documenting performances at the Giza Plateau in September 1978.
He also contributed horn arrangements and uncredited organ and additional production to Shakedown Street (1978) following the departure of nominal producer Lowell George.