His family announced the death on his website. A spokesman said the cause was liver disease; Mr. Bruce had received a liver transplant several years ago.
Mr. Bruce was well known in British rock and blues circles but virtually unknown in the United States when he teamed with the guitarist Eric Clapton and the drummer Ginger Baker to form Cream in 1966.
One of the first of the so-called power trios — the Jimi Hendrix Experience soon followed in its wake — Cream had its roots in the blues and became known for Mr. Clapton’s long, virtuosic solos on reworked versions of blues standards like “Crossroads” and “Spoonful.”
“Those original blues records had been done so well, which meant you could only ever be second best,” Mr. Bruce was quoted in the booklet for a 1997 Cream compilation CD. “But if you treated those songs with a great deal of love and respect, you could remake them into your own.”There were also many original compositions in Cream’s repertoire, most of them — including the hits “Sunshine of Your Love,” “I Feel Free” and “White Room” — written by Mr. Bruce, usually with lyrics by the poet Pete Brown. (“Sunshine,” the group’s biggest hit, was a rare Bruce-Brown-Clapton collaboration.)
Mr. Bruce did most of the singing, in a polished tenor that could be both powerful and plaintive, and his fluid playing provided a solid counterpoint to Mr. Baker’s explosive drumming and Mr. Clapton’s guitar pyrotechnics. His inventive introductions to songs like “Badge” were an essential part of Cream’s sound. Roger Waters of Pink Floyd recently called Mr. Bruce “probably the most musically gifted bass player who’s ever been.”
Cream enjoyed almost immediate success but did not last long. Friction between Mr. Bruce and Mr. Baker is the reason most often cited for the group’s breakup in 1968, after touring extensively and releasing four albums whose total sales have been estimated at 35 million.
Mr. Clapton and Mr. Baker soon reunited and joined with the keyboardist and guitarist Steve Winwood and the bassist Ric Grech to form the group Blind Faith. Despite high expectations, Blind Faith proved to be even more short-lived than Cream, disbanding after one album and one tour. Mr. Bruce, meanwhile, was charting a more ambitious if less commercial musical course.
He recorded a jazz album, “Things We Like,” shortly before Cream disbanded, although it was not released until after an album in a more conventional rock vein, “Songs for a Tailor,” which he recorded after the breakup. He briefly toured with the guitarist Larry Coryell and the drummer and former Hendrix sideman Mitch Mitchell, and then joined the drummer Tony Williams’s pioneering jazz-rock band, Lifetime, alongside the guitarist John McLaughlin and the organist Larry Young.
Mr. Bruce later led several groups of his own and co-led bands with the guitarist Robin Trower and with the guitarist Leslie West and the drummer Corky Laing. He was also an occasional member of Ringo Starr’s All-Starr Band.
Among the albums on which Mr. Bruce played were the experimental Carla Bley-Paul Haines jazz-rock opera “Escalator Over the Hill” (on which he also sang), Lou Reed’s “Berlin” and Frank Zappa’s “Apostrophe,” whose title track was a Zappa-Bruce co-composition. He recorded more than a dozen albums as a leader; the most recent, “Silver Rails,” was released this year.
John Symon Asher Bruce was born in Glasgow, Scotland, on May 14, 1943. He studied cello and composition at the Royal Scottish Academy of Music.
“Growing up, I had envisioned being some kind of a Mozart,” he once said. “I studied classical music early on, and composed a string quartet at age 11.”
But he became disenchanted with the formal study of music and left the academy after a few months. He moved first to Italy and then to England, where he joined the band Blues Incorporated in 1962. The next year he joined the organist Graham Bond’s band, the Graham Bond Organisation, whose members also included Mr. McLaughlin and Mr. Baker. He later had brief stints in John Mayall’s Blues Breakers — where he first worked with Mr. Clapton — and the pop group Manfred Mann.
Cream was inducted into the Rock and Roll Hall of Fame in 1993, and received a lifetime achievement Grammy in 2006. In 2005, the band reunited for concerts in London and New York.
Mr. Bruce’s survivors include his wife, Margrit, as well as four children and a granddaughter.
