Odds are, it was totally impromptu based on what happened next.

You thought I was gonna play a Tenacious D song, didnt ya?

Grohl quipped as he strummed and Rami Jaffee joined him with a bit of accordion accompaniment.

US musician Dave Grohl of rock band Foo Fighters performs on the Orange Stage at Roskilde Festival on July 5, 2024 in Roskilde, Denmark. (Photo by Helle Arensbak / Ritzau Scanpix / AFP) / Denmark OUT (Photo by HELLE ARENSBAK/Ritzau Scanpix/AFP via Getty Images)

Dave Grohl performing with Foo Fighters at the 2024 Roskilde Festival.HELLE ARENSBAK/Ritzau Scanpix/AFP/Getty Images