All Tomorrow's Petty is not a "tribute" band, per se. It is a (part of a) night that you spend with your friends in (or near) a bar or some other celebratory site/occasion. While you're there, you hear a bunch of songs written by Tom Petty and played by people who apparently enjoy playing pretty much anything together. If you already like Tom Petty's songs, you're happy to hear them rendered in a mostly recognizable fashion. If you are deluded into thinking you don't know or like any Petty songs, you are forced to confront this wrongheaded notion.
You might drink, you might not. You might sing, you might not. You will absolutely hear electric guitar. You will not hear the lyrics to "Free Fallin'" (sorry). You will wear whatever the hell you want. Questions may be volleyed by any and all means with the eternal promise of a sincere (if not always prompt) answer. For reasons both legal and metaphysical, there will never be an All Tomorrow’s Petty “album” but you can hear its members playing their own music with Minneapolis-based ensembles such as Halloween, Alaska, Haley, Alpha Consumer, Robert Skoro, The Pines, Gramma’s Boyfriend, Fat Kid Wednesdays, and a whole bunch of others.