The Foo Fighters' Dave Grohl made a surprise appearance during the Harley-Davidson anniversary celebration in Milwaukee.
He played with self-proclaimed "'70s dirt rock cover band" Chevy Metal on the Summerfest grounds Thursday evening.
The Milwaukee Journal Sentinel reported he joked he was there because Chevy Metal needed someone who liked to talk a lot between songs.
In reality, Metal drummer and vocalist, Taylor Hawkins, is the Foo Fighters drummer.
Their songs Thursday night included Van Halen's "Panama" and the Rolling Stones' "Miss You."
Grohl also had posted on his Facebook page earlier Thursday that he was in town.
Another famous rocker, Joan Jett, was in the audience.
More than 100,000 people from around the globe were expected to take part in weekend concerts, parade, street parties and other events.