The Grammy-nominated indie rockers announced details of the Los Angeles theater show just 12 hours before taking the stage. By James Montgomery Arcade Fire’s Win Butler Photo: Getty Images LOS ANGELES — It wasn’t the Grammys, and it wasn’t supposed to be. On Friday night, far away from the machinations of the music industry and the glad-handling of golden gramophones, in a grand old theater that now doubles as the Ukrainian Culture Center of Greater Los Angeles, Arcade Fire — the indie band who, at Sunday’s 53rd Grammy Awards , will face off against the likes of Eminem and Lady Gaga for Album of the Year — threw what will probably go down as the week’s greatest un-official, anti-Grammy pre-party: a sweaty, exuberant, all-ages secret show that felt about a million miles removed from the award-show hysteria that has descended on much of the city. Only 500 tickets were sold, in a first-come, first-serve basis at three locations (a pair of record stores and the venerable El Rey Theatre) on Friday afternoon. There was no red carpet outside or a VIP area inside, just the still-elaborate eaves of an 86-year-old building now crumbling away on a decidedly gritty stretch of Melrose Avenue. The band gave away “free drinks and cotton candy” before the show even began. It was, in short, an anti-industry affair in all conceivable ways, and Arcade Fire savored every second of it. As the strains of Julie Andrews’ “Lusty Month of May” crackled over the speakers, the Canadian band’s members took to the tiny stage, grinned and then, appropriately enough, blasted headlong into “Month of May,” from their Grammy-nominated The Suburbs, with frontman Win Butler cocking his head and jutting his guitar out into the crowd — who, being so close, gladly reached out and grabbed it. Given that they were playing at full strength — eight in all, sawing and hammering away on a menagerie of violins and keyboards and drums and guitars — and that, for much of the past decade, they’ve been tailoring their sonics to massive festival crowds and cavernous indoor spaces, the sound they produced in this little theater was enormous; it washed over the audience, all the way to the back of the building, and then up to the arched ceilings. And that only added to the euphoria. Because there truly is something to be said about seeing a band this big in a venue this small. Already-massive songs like “Rebellion (Lies)” and “Neighborhood #2 (Laika)” became even larger, the bass rumbled and the strings stabbed, the chanted vocals of R