It's hard to believe that Espers hail from Philadelphia. This compelling sextet's musical roots appear grounded in a definitively English strain of fractured, alien folk music: they resemble nothing so much as a psychedelic house band at the court of King Arthur.

The band's mainstay is the preposterously tall Greg Weeks, whose lank locks and all-elbows angularity suggest Joey Ramone in a comfy sweater. Yet his haunting compositions are given wings by Brooke Sietinsons, whose halting voice has the crystalline purity of Maddy Prior's from Steeleye Span.

There are more beards in the packed hall than is usual or strictly necessary, but Espers are no folk-rock period piece. Sietinsons' eerie vocal renders the traditional Black Is the Colour of My True Love's Hair sparse and spectral, like something by the quasi-mystical Gaelic rockers Clannad, before they declined into chocolate box sentimentality.

Weeks is a gawky virtuoso, picking out labyrinthine but lithe guitar lines redolent of Led Zeppelin on the hushed Mansfield and Cyclops. Yet he takes a back seat to the wan Sietenson on the inexorably melancholic Dead Queen, a folk lament whose roots appear to be floating in the ether.

There's a Velvet Underground drone to the trippy madrigal of Cruel Storm, but when Weeks finally sings, on (ahem) Moon Occults the Sun, it is with the keening timbre of Thom Yorke: indeed, were Radiohead to decide to pursue an interesting new neo-folk direction, they would surely sound very like this.

Espers close with a take on Blue Oyster Cult's Flaming Telepaths that turns the bluesy urgency of the original into shadows and memories.

Espers are unlikely to transcend cult status, but they remain a fount of strange and beguiling pleasures.