Who joined Radiohead for “15 Step” when they first played the Grammys, in 2009?

The USC Trojan Marching Band, 36 of them, who played on Fleetwood Mac's “Tusk” in 1979, joined Radiohead's first Grammys performance, of “15 Step”. In rehearsals, which the marching band filmed and later put on YouTube, Thom Yorke told the drummers their snare drums were too busy. In Rainbows won two Grammys that night, 8 February 2009.