At the core of The Doobie Brothers' first lineup was a power combo that would set the stage for their multiple incarnations—and signature sounds—to follow. Founders John Hartman and Tom Johnston worked their Southern-tinged hard rock in biker bars around San Jose, California, before taking on singer Patrick Simmons and bassist Dave Shogren for their self-titled debut. It was just one of many changes that the band would undergo, as their sound progressed to incorporate everything from The Everly Brothers to The Grateful Dead. From their early days on through their later Michael McDonald-fronted years, strong vocals, tight harmonies, and a propulsive rhythm section always kept the Doobies centered and moving forward.