Postponed last year, rescheduled this year—and who knows what the future holds—the Marin Symphony’s collaboration with Grateful Dead guitarist Bob Weir is one of the most anticipated Marin-rock-guy-with-symphony events since Metallica’s S&M. Billed as “First Fusion,” the night ends with an improv jam after a program of Grateful Dead compositions. A rehearsal video of the track “Let It Grow” has made the rounds so far, sounding less like the Boston Pops and more like a rock band (Weir sings). Take bets on the rest of the set list beforehand when the night, a fundraiser for the Marin symphony, gets underway on Saturday, May 7, at the Marin Center. 10 Avenue of the Flags, San Rafael. 8pm. $50–$75.