Everyone loves a free concert, especially on a warm winter day, but fans who went to see Fall Out Boy yesterday in NYC's Washington Square Park almost left disappointed. A paperwork issue forced the band to play without instruments! But the show must go on and that it did. FOB engaged in an a cappella sing-a-long with fans and Pete Wentz captured it all on his video phone and later posted an apology on his blog. "I genuinely feel sorry that we weren't able to play today," Pete writes to fans. "They said if we picked up a guitar we would be sorry ... But we knew this probably was gonna happen. We didn't go through the proper process 'cause we wanted it to be free and fun and spontaneous. So it was our fault. Anyway, thanks for singing with us. We'll make it up to you. It means a lot that you even showed up."

Aw! FOB's new album Folie A Deux hits stores today! Go pick up your copy stat.