Four albums into their career, Oregon quintet the Decemberists look poised to become an overnight success. Despite being a semi-concept album based on an arcane Japanese fable, their new record The Crane Wife has breached the US top 40, while a sold-out Festival Hall testifies to their growing appeal on these shores. It is a notable achievement as, on the surface, the Decemberists appear destined to be cult figures. They play misshapen folk-tinged songs about seafaring, prostitution and the American civil war: 15-minute opening track The Tain deals with the decidedly unpoptastic topic of cattle rustling in Ireland 500 years ago.

The contradictions are inherent in the figure of singer Colin Meloy, who leaps into the audience while looking as if he doesn't have a rock'n'roll bone in his body. The Decemberists are cerebral and idiosyncratic but they don't always connect, frequently losing momentum in a welter of inconsequential noodling. Meloy clearly cut his musical teeth on early 1970s prog rock, and spindly, fixated songs such as You'll Not Fear the Drowning could have nestled easily on King Crimson's In the Court of the Crimson King. The intricacy gets tedious, and it is a relief when singing keyboardist Jenny Conlee comes to the fore on the lop-sided Yankee Bayonet and Belle & Sebastian-esque The Apology Song.

A smirking Meloy conducts a zealous crowd in synchronised high-pitch screaming on the encore of The Mariner's Song, but while the track is typically expansive, it never really goes anywhere. It is an apposite end to a self-indulgent evening; maybe the Decemberists are better off sticking to cult status after all.