There was a time when musicians couldn’t correct mistakes with a computer program. They either rerecorded a song until they got it right or released it as is, complete with slip-ups. It made the music more real. More human. And it’s an era that Dave Grohl eulogizes and celebrates in ‘Sound City,’ a documentary he directed about a Los Angeles recording studio that was state-of-the-art in the 1970s – when Fleetwood Mac, Tom Petty and Neil Young made records there – but closed in 2011, when it became clear that it couldn’t compete with technology on some kid’s laptop.