Maynard James Keenan already conquered the prog-metal scene with Tool in the ‘90s, but the ambitious singer was far from done. Setting his sights on alt-rock, Keenan formed A Perfect Circle with former Tool guitar tech Billy Howerdel, taking the genre by storm in the new millennium with Mer De Noms. It was a debut that channeled Tool's intensity into melodic, layered metal arrangements, a formula that spawned two more hit LPs before the band went on an extended break. Having officially returned to touring at the end of the aughts, APC are poised to reward the patience of their fans.