Keller Williams plays improvisational folk with missionary zeal, injecting so much eager-to-please energy and goofy humor into his performances that even the normally jam-averse might be inspired to go for a twirl. Filling his marathon sets with imaginative makeovers, he finds the dark side of “Moondance,” invents falsetto funk-folk during his rendition of Michael Jackson’s “Don’t Stop ‘Til You Get Enough” and turns Ani DiFranco’s “Freakshow” into a Check Your Head-era Beastie Boys B-side. Not all of his experiments work (his “Rapper’s Delight” makes the Wedding Singer granny’s version seem soulful), but even his failures are hard to hate. Like an unfunny standup comedian who can make people laugh through pure personality, Williams gets fans dancing without the requisite monster grooves. Not content to coast on covers and charisma, Williams smokes on acoustic guitar during his lyrically quirky originals.