One of the two lead guitarists of the psychedelic-era San Francisco band Quicksilver Messenger Service, Gary Duncan, has died, according to confirmed reports by people close to the musician. Duncan, who also served as one of the group’s three primary singers, died Saturday morning in Woodland, Calif., after suffering a seizure and falling into a coma. He was 72.

Born Gary Grubb in San Diego, Duncan joined a band called the Brogues in Merced, Calif., in 1965. The group, which also included drummer Greg Elmore, split that same year and the two musicians accepted an invitation to team with guitarist John Cipollina and singer-songwriter Dino Valenti, who had been working as a traveling folkie. Along with bassist and vocalist David Freiberg and a third guitarist, Jim Murray, they formed the band that would become the San Francisco-based Quicksilver Messenger, but they were immediately reduced to a quintet when Valenti was arrested and jailed for marijuana possession.

Taking their name from the fact that four of the members shared the Virgo astrological sign, ruled by the planet Mercury (a.k.a. quicksilver), the group quickly gained recognition among the first wave of Bay Area psychedelic bands, alongside groups like the Grateful Dead, Jefferson Airplane and Big Brother and the Holding Company. They performed often at the city’s ballrooms, the Fillmore and the Avalon, and at the Monterey Pop Festival in 1967.

Duncan and Cipollina often engaged in fiery, extended jams that showcased their complementary styles, but, as our writer said in a retrospective review, QMS was “a rock ’n’ roll band that’s not only conversant with jazz but also at ease with—and adept at—pop music.”

Quicksilver held out longer than the other major Bay Area bands in signing a recording deal, but finally signed with Capitol Records in late 1967, by which time Murray had left the band. Duncan told an interviewer, “We had no ambition toward making records. We just wanted to have fun, play music and make enough money to be able to afford to smoke pot.”

The remaining quartet released their self-titled debut on the label the following year, followed by the live Happy Trails by the same lineup in early 1969. Duncan temporarily dropped out of the band that same year and did not appear on the third album, Shady Grove, which featured the newly added British pianist Nicky Hopkins. By 1970, not only had Duncan returned, but so too did Valenti, who took over the band’s lead vocal spot for the albums Just for Love, What About Me (both 1970), Quicksilver (1971, with Freiberg, Cipollina and Hopkins now out) and Comin’ Thru (1972). The group split that year, then reunited for Solid Silver in 1975, with Duncan, Cipollina, Freiberg, Elmore and Valenti on board.

Duncan later formed new lineups of Quicksilver (no longer using Messenger Service in the name and sometimes calling it Gary Duncan’s Quicksilver), with which he released several albums beginning in the late ’80s.

Duncan’s death follows those of bandmates Cipollina, Valenti and Murray. Freiberg tours with the current lineup of Jefferson Starship.