Band played two-and-a-half hour set that included four covers
The former Sunny Day Real Estate member has debuted the song 'Believe The Squalor'
Dave Grohl tells crowd: "OK, we got a new Foo Fighters song"
The band played a surprise show at the LA Forum for Dave Grohl's 46th birthday
Band will play benefit gig at Los Angeles Forum on January 10
Band perform track with accompaniment of string orchestra
Group hope cover will lead to Foo Fighters gig in region
Song unearthed in episode of 'Sonic Highways' series
The eight part series accompanied Foo Fighters' recent album of the same name
Season One of the show documented the making of the Foo Fighters' latest album