The Red Hot Chili Peppers decided long ago they were never going to mime a live performance.
But it turns out the band made an exception for the US National Football League.
The group's bassist, Flea, said in a letter to fans posted on the group's website on Tuesday that the Rock and Roll Hall of Fame members pretended to play along to a pre-taped track of Give It Away during the American football championship Super Bowl halftime show as Anthony Kiedis sang live.
The request came from NFL officials who felt it was too difficult to pull off a completely live performance because of possible sound problems.
The admission came after observers noted Flea and his band mates were not plugged in while performing on Sunday at the MetLife Stadium in East Rutherford, New Jersey.
Flea wrote on the band's website that the opportunity was too big for the lifelong football fans to turn down.
After debate, dubiously checking with fellow musicians and consulting with headliner Bruno Mars, they decided it was "a surreal-like, once-in-a-lifetime crazy thing to do and we would just have fun and do it".
The 51-year-old said the group pre-recorded a unique instrumental track for the show.
He did not directly address whether Mars also recorded instrumental tracks for his appearance, though he said Mars was aware they did.
A record 115 million people tuned in to watch Mars and the Peppers, bettering audiences of 114 million for Madonna and 110 million for Beyonce.
- Rock group U2's new single Invisible raised more than US$3 million for the fight against Aids during the 36 hours it was available for free on iTunes, it was revealed on Tuesday, after Bank of America pledged a dollar for every download.
Additional reporting by Agence France-Presse