Cook tweeted a brief apology early Friday, saying he didn’t want any of his new material to hit the airwaves yet.
That didn’t pacify critics, including several who asked on Twitter why Cook chose to do a new set at a charity event.
Cook’s representatives didn’t immediately respond to requests for comment.
The overnight Boston Strong Concert featured acts including Aerosmith, James Taylor, Jimmy Buffett and Boys II Men. The show raised money for The One Fund, the compensation fund established by Gov. Deval Patrick and Mayor Thomas Menino to help bombing victims.