The British and US bands, who are touring America together, were persuaded to give the crowd a tune by two guitar players who were drinking at the bar.
But Kaiser Chiefs' frontman Ricky Wilson missed out on the spontaneous event as he had elected to go to bed early.
He says, "NICK (HODGSON, drummer) and SIMON (HIX, bassist) were going to a pub across the road from the venue and it's just full of people at the end of the show.
"And Dave Grohl (Foo Fighters) goes with them and just walks up and has a drink.
"Then apparently there were these two acoustic guitar guys and Dave did EVERLONG with one of them.
"And then Nick, Simon and Dave played I PREDICT A RIOT at the bar.
"Yeah I think that was the wrong time to take an early night."