See Foo Fighters Lead Orchestra in Dramatic 'I Am a River' for 'Fallon'

The rockers treated the 'Tonight Show' audience to a dramatic rendition of the closing track on 'Sonic Highways'

The Foo Fighters' latest stop on the Sonic Highways promotional tour brought them to The Tonight Show where they delivered a smashing, Herculean performance of album closer, "I Am a River."

The track starts out small, with frontman Dave Grohl crooning a tale of finding salvation underground, while he and guitarists Pat Smear and Chris Shiflett create a simple six-string pulse. But soon enough, the track burst open with Grohl howling "I am a river!" as the band was joined by a sizable orchestra, who help bring the song to its cinematic conclusion.

The Foo Fighters played "I Am a River" for the first time live during a marathon set at Irving Plaza in New York City earlier this month. Beforehand, the group screened the final, New York-centric episode of Sonic Highways — the HBO documentary series accompanying the album — which chronicled the city's sprawling music history, and the recording of "I Am a River."

Grohl discussed why he chose to end Sonic Highways with a special hour-long episode about New York during an interview with Rolling Stone. "This place is unlike anywhere else," he said. "Everything that we talked about in the entire series all comes to conclusion here, because New York City has it all whether it's talking about inspiration or community or industry or gentrification or creativity or survival or starting over."

Beyond New York, the singer discussed a wide range of topics in Rolling Stone's recent cover story on Grohl, from the support his mother gave him as a young musician to how he unwinds after a day of taking care of his three daughters (it involves wine, no pants and monster riffs), as well as his plans for the next Foo Fighters record.

Next year, the Foos will embark on a massive North American tour, which they will kick off with a Fourth of July shindig in Washington, D.C. That show, which will celebrate the band's 20th anniversary, will feature performances by musicians representing some of the cities it chronicled in Sonic Highways, including Chicago's Buddy Guy, Austin's Gary Clark Jr., Seattle's Heart, Los Angeles' Joan Jett and the Blackhearts, New York City's LL Cool J with DJ Z-Trip, D.C.'s Trouble Funk and New Orleans' Trombone Shorty.