Bob Weir and RatDog | RatDog.Org

Robin Sylvester is what they call a working musician. And right now he's got the best job he's ever had. The 52-year-old London-born bassist has been hired to replace Rob Wasserman in RatDog, the band headed by erstwhile Grateful Dead guitarist/singer Bob Weir.

"I didn't expect to join a band and go on the road at my age," he said one recent afternoon at the Grateful Dead's rehearsal studio in Novato. "I wouldn't have foreseen this, but I couldn't have planned it better."

Sylvester will make his Marin debut with RatDog tomorrow when the band headlines the Marin Music Festival (11 a.m. to 7 p.m.) at Lagoon Park in San Rafael. He's been a fan of the Grateful Dead since he was a teenager in England, playing 1968's "Anthem of the Sun," as he put it, until the grooves wore out.

With his hippie-length hair and his trademark black Converse sneakers with psychedelic-colored laces, he looks like a longtime member of the Dead's extended family. In reality, he'd met Weir only casually before joining his band.

"We shook hands a couple of times, but I'd never played with him," Sylvester said in his genteel English accent, allowing, though, that he has played with just about everyone else.

Sylvester grew up in what he calls swingin' London, beginning as sound engineer, then, inspired by Paul McCartney, taking up the bass. He toured with British blues diva Dana Gillespie, joined a short-lived '70s band the Movies, then settled down as a session musician, first in Los Angeles, then in San Francisco, living for 20 years in the same place in Bernal Heights until moving recently to Sebastopol.

For much of his career, he was a colleague of the late saxophonist Steve Douglas, whom he describes as the last of the old school session players. With Douglas, he worked with the Beach Boys, Phil Spector and Ry Cooder. During the summers, he made a living playing corporate concerts and county fairs -- money gigs to pay the bills -- with acts like Billy Preston, the Coasters, Mary Wells, Del Shannon, the Marvelettes and Peter Noone of Herman's Hermits.

The RatDog job opened up earlier this year when Wasserman parted ways with the band he co-founded with Weir after they had played together as an acoustic duo. A renowned standup bassist, Wasserman is a virtuoso on an acoustic instrument that is a rarity in an electric rock band. Rob has always been sort of a square peg, and RatDog turned into a round hole, Weir has been quoted as saying.

"They wanted to make the move to electric, so I never felt like I was filling Rob's shoes," Sylvester told me, adding that he couldn't be happier about joining an established band with a loyal following. "There were times on the road when I was doing cartwheels down the hall at the hotel," he said. "To work for 20 years and finally have a job where they respect you and treat you well doesn't happen very often, especially to a musician at my point in life."