After one homemade LP and three years of tour dates across North America, Shakey Graves finally has a genuine, studio-produced album coming out in October and a rousing single released already. At every show, the singer-songwriter brings together folk, bluegrass and a rough-hewn rock ’n’ roll edge—but he doesn’t bring along much else. Usually, it’s just him onstage, playing with only his guitar and a kick drum carried in a suitcase, and with enough energy to match a full-sized band. And he rarely plays his songs the same way twice. The result is an endlessly inventive and surprising live show, which, when coupled with his self-effacing banter, has helped cultivate a fiercely loyal following. Few but Shakey have managed, as he has, to inspire such devotion from fans that it can make friends from the strangers in his audience. Oct. 21 at the Hamilton. Sold out.