“Our story is really fundamental to Relix,” says Roger McNamee, reflecting on the formation of Doobie Decibel System. “Those of us who live in the Bay Area are blessed to have venues by Bob Weir and Phil Lesh. San Francisco hadn’t been interested in up-and-coming bands for a long time, but Sweetwater and Terrapin Crossroads completely changed that through ‘friends nights’—improvisational evenings featuring different people from the local scene.”

It was in this context that McNamee first met Jason Crosby (Assembly of Dust, Robert Randolph, God Street Wine, Lesh, Weir), who had recently relocated from the East Coast. McNamee invited Crosby to sit in with Moonalice at Sweetwater. This, in turn, led Crosby to McNamee’s house, where the pair shared a revelatory moment after they opened a book of Beatles sheet music and arbitrarily performed “Two of Us.”

“Now, keep in mind that my wife [Ann] has a Ph.D. in music theory—she’s a retired college professor,” McNamee explains. “We’re playing out on the porch, and she peeks her head out and says, ‘Is that you guys? More like that, please.’ So Jason flips the book randomly to ‘Dig a Pony,’ and she comes back five minutes later and tells us, ‘Guys, you need to record this. You need to hear what’s going on.’ What she had noticed was there was something about the pairing of my voice with Jason’s, where we create this harmonic resonance where your ear hears this third part. At this point, we were 20 minutes into never having played together as a duo before.”

That casual porch session led to a new, more formal musical partnership. Their name, a riff on the library classification system, was Crosby’s own term for the method he employs to keep track of the songs he performs with so many different acts.

The pair hit an early snag after McNamee received an irate call from The Doobie Brothers manager, who claimed trademark infringement (a questionable assertion, as the legal standard is whether a competing name “causes confusion, deception or mistake”). However, the musicians reconciled at Lockn’ 2015 after Doobie Brothers cofounder Tom Johnston offered what McNamee characterizes as the “nicest apology I’ve ever received in my entire life.”

While Doobie Decibel System began as a two-piece, the group performed at this year’s Lockn’ as a quintet, with ALO guitarist Lebo, longtime Weir drummer Jay Lane and Bay Area mainstay and multi-instrumentalist Pete Sears. (DDS also gigs as a trio with Lebo.) The band’s shows are archived on its robust website and, as McNamee notes, in all three iterations, “tight harmony is an essential part of what we do. The fundamentally acoustic foundation of the music is quite distinct from Moonalice, which is pretty clearly a jamband. This is where I say I am not worthy with respect to my dear friends Phil Lesh and Bob Weir. The thing they have created has empowered a lot of musicians and created an audience who are open to this flow of music.”