Acclaimed British folk artist Laura Marling performed at the 6th & I Synagogue in Washington D.C. Marling, just 21 years-old, has already been nominated twice for the Mercury Music Prize and won Best Female Solo Artist at the 2011 Brit Awards. (Kyle Gustafson/FTWP)

The panel of British musicians and industry figures that awards the Mercury Prize each year recognizes the British act that released the best album — not the one that’s most electrifying in live performance. At the ripe age of 21, folk singer Laura Marling has already been nominated twice.

The baroque, wintry balladry that made up her 80-minute headlining set Monday at Sixth and I Historic Synagogue felt made-to-order to assuage the anxieties of awards-pickers: It was accomplished and skillfully wrought by a five-piece band that burnished Marling’s silvery voice and guitar with cello, banjo and French horn.

But there was something standoffish about the whole thing. And for a performer who conceded right at the top that “stage banter is not my forte,” Marling sure did go on, dissipating much of the spell her ageless, melancholy vocals — poised in some seaborne sonic longitude between Regina Spektor and Joni Mitchell — cast in that beautiful house of worship, with its vaulted ceilings and somber stained glass.

After 45 minutes, she dismissed her band to play a pair of solo numbers. The haunting “Goodbye, England (Covered in Snow)” was elegiac and vulnerable, pushing her to the low end of her range. “I find it excruciatingly self-indulgent when singers play new songs that no one has had a chance to hear yet,” she opined a few minutes later, by way of introducing a new song no one had had a chance to hear yet.

It wasn’t excruciating or self-indulgent, though it did lack the pith of her closer, “All My Rage,” wherein she repeats, “All my rage been gone /I leave my rage to the sea and the sun.” But bit more rage would make her a less opaque performer, and probably a more exciting one, too.

Klimek is a freelance writer.