Belle & Sebastian preserves a varied if quirky heritage

Belle & Sebastian is keeper of a musical heritage that exists only in its imagination. The Scottish ensemble of course draws on a wide, disparate range of sources: light ‘60s pop, dark Velvet Underground riffing, the lush strings of easy listening.

But the resulting sound is somehow both modern and ancient, dated and seemingly timeless, as if reflecting a musical genre that never was.

So at the Greek Theatre on Sunday, the band was alternately rocked up and as soft as a plush toy.

With up to a dozen players on stage at any time, Belle & Sebastian crafted deep, complex arrangements, where every piece seemed crucial to the whole, endlessly soothing and alert.

The band sketched out the broadest definition of pop during “Expectations,” a 1996 song whose gentle urgency was underlined by quick trumpet squeals. Elsewhere, the band created waves of pop under the influence of Brian Wilson, with French horn tangling with guitar.

Singer Stuart Murdoch was not the most dynamic frontman, but his charming, gentle manner was a nice change of pace and well-suited to the music and mood. He hopped comfortably behind the microphone in his blond Caesar haircut and white jeans, once stopping mid-lyric to aim a quick “Shhh!” at an over-excited fan.

Murdoch paused to consider the crowd, wondering if “you might want to settle back tonight, or if you want to dance. I’m trying to adjust the mood tonight.”

Support act Bright Eyes has spent most of its career playing to smaller club crowds, but leader Conor Oberst never seemed lost on the big stage. Most of the band’s set had seven players behind the young singer-songwriter, each adding layers of sound and feeling, but the truth was that the man could have been there alone with his acoustic guitar, picking and slashing, and easily have carried the night.

Oberst’s voice frequently rose from a quiver to a scream, expressing a variety of emotions: delicate, vulnerable, determined. The melodies were disarmingly simple, a few chords and a feeling of desperation. It was pop-rock-folk at its richest and most moving, transforming uncertainty into nirvana.