John Darnielle, the man behind the Mountain Goats, might be the reigning nerd in all of indie-rock geekdom. He's got squeaky voice, even by emo standards; an awkward, school-kid haircut; and most damning of all, a thoughtful blog, Last Plane to Jakarta, often frequented by rock critics. Last night at Studio B, he not only presented a typically engrossing set of his wordy songs — he gave them all wordy (bloggy?) introductions. Many of his early tunes took shape, he said, while daydreaming in college. As lesser students posed dumb questions in the open-floor sessions that closed lectures, he would jot down lyrics in his notebook. (The track “Grendel's Mother”? A response to English classmates mystified by Beowulf.) Later, in the midst of three welcome but decidedly un-rock-star encores, the band presented their Über-geeky live trademark, an earnest — heartfelt, even! — cover of the chirpy Ace of Bass hit “I Saw the Sign.” And the class, of course, sang along. —Brandon Cuicchi