Here is why you must tune into the Grammys on Sunday: Radiohead is playing "15 Step" with the USC marching band. I've been told it's okay to talk about this now (somebody else already leaked it), and how I wish all of you could have been here at Staples with me this morning to watch Thom Yorke, Jonny Greenwood, and three dozen elated college kids take an already very good song and turn it into a jubilant, slightly menacing masterpiece. We're talking "I would pay money to buy that off iTunes" good. "I will keep that performance on my DVR to watch on sad days" good. "Please make the song into a vacation resort because I want to go to there good." It is so. cool.

When I walked in at 9 a.m., there were already tubas glinting under the shiny, American Idol-style metal gridwork of the space stage, the thunder of the rhythm section bouncing around like buckshot. They did a rough run-through with crew and directors clustered on stage, after which Yorke politely asked, "Can you make my voice sound a little less shiny? I like the idea that I've got to belt it out over these guys, you see." Between takes, he beatboxed a bit into the mic; the band kids sat on the risers and mostly just grinned in disbelief. Yorke wandered down to the lip of the orchestra pit and asked a nearby stage manager, "Is it okay if I stand here?" Sure, said the guy, "but just so you know" -- he gestured to the floor beneath Thom's feet -- "this is a wall that comes out of the ground." Thom took a step back. "All right! Here we go! Standby!" said another stage manager, and the wall did indeed come up. The band members stirred with excitement. A stand-in who was not Gwyneth Paltrow began reading the intro off the teleprompter, and by the time she got to "Nominated tonight for Album of the Year..." the wall had lowered again to reveal Thom making a my-head-is-exploding gesture to Johnny, I assume because even Thom Yorke still gets jazzed about the Grammys. And then a snare drummer in the front row counted things off, the bass players raised their sticks, and the awesomeness began.

After the jump, I talk to one of the USC students, and run down rehearsals from Carrie Underwood, the Jonas Brothers (with Stevie Wonder!), Taylor Swift, and Miley Cyrus...

Mad props to the USC kids for their talent and their stylish choreography, but mostly for being totally professional in a situation that would have reduced many grown men to pudding. Their directors just finished making tweaks to the musical arrangement last night, and tomorrow they'll be playing with arguably the best band in the world on national TV, yet they completed take after take of the complicated rhythms with incredible poise. "Ecstatic" is how 19 year old Kelsey Anderson (communications major; bass drum) summed up the feeling of getting this gig. Her eyes had the slightly glassy look you see in people who have recently experienced a religious conversion, or seen the face of God. "I went out and bought In Rainbows on vinyl for Thom to sign. He wrote my name on it. I'm gonna keep it forever." She was highly complimentary of the spiky-haired frontman, with whom they apparently had robot dance-offs in rehearsal. "He's surprisingly down to earth, fun, and amazing to work with," Anderson said. "Some people you think might have big egos, but he doesn't. We we were just in awe of him." As for whether her life has now peaked at 19, she laughed and said, "This is pretty much the coolest thing I've done so far."