CAMBRIDGE - Operating under the moniker Neutral Milk Hotel, Jeff Mangum recorded two albums - one of which, “In the Aeroplane Over the Sea,’’ rapidly revealed itself as one of the best of its era - and then vanished for a dozen years.
As a result, all Mangum has to do to wring fervent applause out of his devoted cult following is walk onstage. That’s precisely what happened Friday night at Sanders Theatre, where a sold-out crowd that included fellow musical explorer Amanda Palmer gave Mangum a hero’s welcome just for showing up.
But despite a set list limited to those two albums and a cover of Roky Erickson’s simple and sweet “I Love the Living You,’’ Mangum (who played another sold-out performance Saturday night at Jordan Hall) wasn’t simply coasting on his legend. That was clear from the start, when he grabbed a guitar and played “Oh Comely’’ with a dark and deliberate intensity that made it seem like his disappearing act never happened.
Mangum kept that intensity up, staring with laser focus at the back wall as he sang in his declamatory, full-throated yelp. But he softened enough to flash brief, earnest smiles with every round of applause, and when his microphone failed during “A Baby for Pree,’’ he casually stepped out of his chair and kneeled at the lip of the stage, all while continuing the song without amplification.
Since “Aeroplane’’ is, at its core, just a man with an acoustic guitar, the material didn’t require much simplification for a solo concert. Even so, he occasionally encouraged the audience to sing along, turning “The King of Carrot Flowers’’ and “Holland, 1945’’ into cracked hootenannies.
After quietly ending “Engine,’’ Mangum left with a gracious “Thank you, good night.’’ The house lights came up, the doors opened . . . and after a five-minute standing ovation, Mangum returned for a concert rarity: a genuine, unplanned encore. Off-mike once more, he launched into the frantic strumming of “Two-Headed Boy’’ as the audience sang softly along until the aching slowdown at the end. That was left to Mangum alone.
String quartet American Contemporary Music Ensemble (ACME) opened. Three Erik Satie pieces set the tone, with “Gymnopédies’’ providing a slow, delicate rise and fall, and Gavin Bryars’s “Jesus’ Blood Never Failed Me Yet’’ was stunning, using heavy repetition to transform a street person’s a cappella song into mournful but transcendent ecstasy.