Somewhere along the way, Dave Grohl has become the unofficial Mayor of Rock 'n' Roll: a gregarious ambassador who wins armloads of Grammys and even directs a documentary -- Sound City: Real to Reel -- about the artistry, technology and magic that goes into making a great studio recording. So it makes sense that Grohl would address the assembled music fans at the SXSW music conference for the year's keynote speech.

In a wide-ranging address that started with a nod to last year's rousing keynote by Bruce Springsteen, Grohl tells the story of his punk education (with its genesis at the Cubby Bear in Chicago and launch pad at the 1983 Rock Against Reagan rally in D.C.) and how, over the course of a career with many stages, he learned, as he put it again and again, that "the musician comes first."

It's a message Grohl returns to again and again in the speech, through the story of Nirvana's explosion, destruction, the birth of Foo Fighters and the creation of his new movie. External forces, he says -- whether major label expectations or the "ethically suffocating punk underground" -- dilute the purity of a musician's sole asset. "It's your voice," he says. "Everyone's blessed with at least that. And who knows how long it will last?"

At 44, Grohl exudes youthful exuberance even as his music career approaches the three-decade mark -- he joined the D.C. hardcore band Scream at 17 -- and he remains a prolific and adventurous collaborator. He's particularly fond of supergroups, having formed Them Crooked Vultures (with Led Zeppelin's John Paul Jones and Josh Homme from Queens of the Stone Age) and Probot, featuring an all-star lineup of metal musicians. In short, the guy pops up everywhere, and works with everybody.

His is a career that probably should contribute to a massively inflated ego, but Grohl's affability is a central trait, whether he's tweaking "blooooogs" or the pop hits of the early 1990s, before Nirvana hit it big. Or himself. He's not the world's best drummer, he insists, not close to its best singer/songwriter. The secret to his success: "I've been left alone to find my voice since that day I heard Edgar Winter's 'Frankenstein.'"