Foo Fighters' appearance on 'The Tonight Show Starring Jimmy Fallon' finally aired last night (Dec. 18) after the original episode was canceled following the birth of Fallon's second daughter. The band performed the 'Sonic Highways' track 'I Am a River' for 'The Tonight Show' viewing audience.

The track started off with an understated melodic opening before building in intensity as the performance continued, and by the end Foo Fighters were rocking out with a full string orchestra backing them. You can watch the performance above.

It appears likely that the Foos actually recorded their performance a few weeks back during their regularly scheduled appearance. In the video from the show, Jimmy Fallon introduced the band from the audience and was spotted in the crowd after the performance rather than his usual greeting of the performer. The band was scheduled to appear the week that Fallon had to cancel a few episodes at the last minute when he welcomed his second child.

Meanwhile, in other news, Foo Fighters frontman Dave Grohl will turn up on the upcoming debut disc from star-studded new project Teenage Time Killer. The project features Corrosion of Conformity's Reed Mullin playing alongside a number of well-known musicians including Grohl, Lamb of God's Randy Blythe, Slipknot / Stone Sour frontman Corey Taylor and more. Teenage Time Killer just inked a deal with Rise Records, but an official street date has not been announced. In addition to making a guest appearance, Grohl lent his Studio 606 for the recording of the album. Stay tuned for more details.

You Think You Know Foo Fighters?