Kristian Matsson, the smallish Swede who performs under the moniker The Tallest Man on Earth, sings, plays guitar and occasionally takes a turn at the piano. That's all there is to his act: no backing band, no frills. Heck, he barely needs amplification, given the volume at which he performs. But that right there — the gigantic force of his delivery, the percussive hyper-dexterity of his playing — is part of what makes him so magnetic on stage. On paper, he's just another poet strumming a guitar.