The most striking thing at Union Transfer on Wednesday night wasn't Joanna Newsom's performance, although her intricate harp-centered compositions and protean vocal delivery never failed to surprise.

It was the quiet.

With Newsom on harp or grand piano and a three-piece band playing keyboards, drums, and a variety of stringed instruments familiar and exotic, the ensemble's collective volume never rose above a low roar. But the sold-out crowd stayed hushed, barely talking above a whisper, even between songs.

The audience's stillness speaks to the reverence Newsom has accrued over the course of the last 11 years and four albums, the most recent of which, Divers, was released in October. What began on her first self-released EPs as sprightly, folk-tinged romps grew into sprawling, multi-part opuses that constantly slip between ether and earth. Her voice leaps between octaves - or make that voices, ranging from a childlike croak to an airy warble. Violinist Mirabai Peart coaxed the audience to clap in time during the set's final song, but they never sang along, perhaps because they dared not try.

Although Newsom grew up around Philip Glass and lives, with her husband, actor Andy Samberg, in a Hollywood mansion once occupied by Charlie Chaplin and Mary Astor, she remains disarmingly down-to-earth on stage. She joked that she'd consider the show a raging success if she could get through it without tripping over her dress or a stray viola. (Such are the perils of indie chamber music.)

But her musical ambitions are dazzling, almost daunting. Divers is a concept album. Even though characters like the Rufous Nightjar who turns up in "Anecdotes" and "Time, as a Symptom," recur, Divers' organizing principle is not narrative or thematic but musical. The album is built around an obscure system of harmonic notation. You need both a lyric sheet and an Internet connection to decipher lyrics like "Areion, Rharian, go free and graze," but the sound of the words seems more important than attempting to decipher their meaning. You're never done trying to figure them out, which may be why her audience kept so quiet. They were actually listening.