The album features the Foo Fighters' first instrumental, "Ballad of the Beaconsfield Miners". It was written by Grohl after meeting with one of the miners involved in the Beaconsfield mine collapse who requested an iPod with "In Your Honor" in it during the incident. As Grohl was moved by this action, he decided to "write something just to dedicate to him that night because he definitely seemed like a hero", and later promised to include the instrumental on the album. The album version features Kaki King, whom Grohl invited to record the song as she was visiting Studio 606. Grohl later said that "I showed it to her once, and she shredded 10 times better than I ever played it". Another guest was guitarist Pat Smear, who had been a bandmember from 1995 to 1998, and a guest musician on the tour for "In Your Honor". Smear, who has since been reinstated as a full-on member, described his participation as "the oddest recording experience I had with Foo Fighters" given he had no input in composition and was "going in and playing on a song that was already written". This is their first Foo Fighters' album, since "The Colour and the Shape" (1997) to feature Smear, before officially rejoining the band for their next album, "Wasting Light" in 2011.