Sound City, Grohl recalls, "was a very special place where musicians went to get a natural sound in order to create a performance vibe for their album. Even as kids in Nirvana, we were aware of its reputation. You'd go there, plug in and just go for it.
"They closed because they mainly did analogue recording, and that became out of date. But those 15 days I spent recording at Sound City with Nirvana changed my life. If we hadn't achieved that raw sound with Nevermind, we may never have sold that many albums, and the chances are I wouldn't be sitting here today.
"That mixing console of theirs was as important to me as any band I've ever been in, and I was heartbroken when I heard the studio was closing. I said, 'If you ever want to sell that mixing desk I'd love to have it'."
The film began as a tribute. Grohl moved the Neve console - one of just a few in the world - into his own home in Los Angeles "and then I invited a few friends to come and jam with me".
Thanks to a musical pedigree which includes spearheading grunge, Grohl's "friends" are more high-profile than the average documentary maker's.
"I am lucky in that I have a lot of friends in the music business, and they know that I am energetic and enthusiastic when it comes to playing. So I can say to Rick Springfield, 'Dude, let's do a song together', and he'll come over."
Did he approach McCartney in the same breezy manner? Grohl guffaws. "Yeah, exactly those words."
Of all the sessions captured in Sound City, McCartney's is the most interesting. Nirvana producer Butch Vig is at the mixing console, with Grohl and Nirvana bassist Krist Novoselic also present. It's like watching Macca in a personal training session.
They coax a performance out of him until he sweats. The result is a track ironically called Cut Me Some Slack, McCartney at his rawest in years.
Other collaborations are diverse; from Nine Inch Nails' Trent Reznor, and Slipknot's Corey Taylor to Fleetwood Mac's Stevie Nicks. Grohl's ultimate goal is spreading the gospel of "real music". "I want to inspire others," he enthuses. "I don't want the next generation to think that you have to go to school to study music or be a computer programmer in order to be in a band. I want them to know that you can buy a guitar that's a piece of junk and still write great songs and become the biggest band in the world. That's what rock 'n' roll is all about."
Not, presumably, about going on TV shows to achieve a dream? Grohl considers. "I think that anyone who has the balls to go and sing their heart out on stage is awesome. But I want my daughters to understand that music isn't a contest. I never want for them to sing a song, and to be told, 'That isn't good enough'. Because I would never say that; I would say, 'That's killer. Do it again, write something else'. I would never want to discourage any other artist or musician because I don't think that is cool. It doesn't inspire others.
"It's not like it hasn't happened to me. I remember I tried out for The King and I in seventh grade and was offered the part of understudy," he laughs. "I was like: 'Understudy? Understudy? You have got to be kidding me! I am never going to be an understudy'."
To a certain extent, Grohl's Midas touch is down to today's cult of personality; few others in the industry combine his affability and eloquence.
Although his first marriage to photographer Jennifer Youngblood ended in 1997, he's been lucky in love second time around; he has two daughters, Violet and Harper, with his wife Jordyn Blum, who he married in 2003. His blessed and busy life he says, is inspired by Kurt Cobain.
"When Kurt died, I realised that every day should be celebrated in some way, and we're so lucky to have what we have. It doesn't matter if it's the best or the worst day of your life, just being here is good enough. So I really try to take advantage of it. Hey, I am busy but sleep is overrated. You know, I have so much energy and I don't even do drugs. It's honestly all done on coffee."
Next, Grohl says he'll return to his primary focus, Foo Fighters. "We're on hiatus, which our guitarist Pat Smears calls 'I hate us', so we're backed off and getting ready to do the next album. But for everyone who does think I am Amish, or I can't use a computer, I'd like them to know that my iPhone ..." he digs it out of his pocket, "has about 50 new Foo Fighters songs on it, because every time I come up with a new idea, I hit record."
He suddenly looks extraordinarily pleased with himself. "How cool is that?"
Who: Dave Grohl, Foo Fighter turned rockumentarian
What: Sound City, his doco about the Los Angeles recording studio and musical creativity
When:Out now on DVD and download, along with new album recorded for the film featuring Grohl, Paul McCartney, Stevie Nicks, Trent Reznor and more.
- TimeOut / Independent
