The Tonight Show was one of the few places the Foo Fighters hadn’t appeared on during their massive promotional tour for Sonic Highways, but that changed Thursday night when Dave Grohl and Co. dropped by to perform “I Am a River” for Jimmy Fallon. The song hums along with the Foo’s usual energy, until it explodes at the end when they’re joined by an entire string section. The violinists help bring the track to a soaring conclusion, which you can watch above.