Who are they? A London-based folk-rock ensemble led by Marcus Mumford, featuring loads of banjo, mandolin and accordion. Its debut, "Sigh No More," came out stateside in February on Glassnote, the label behind Phoenix's breakthrough disc.

Why the buzz? "Sigh" has already gone platinum in Britain since its October release there. Another British high-water mark, Kinks legend Ray Davies has recruited the band to collaborate on an upcoming album. Locally, the show has been sold out for months, and the single "Little Lion Man" has repetitively tested the Current 89.3 censor button with its hook, "I really [bleeped] it up this time" (the rare case where the station has arguably overplayed a song).

What do we think? Mumford certainly stands out as one of England's most promising singer/songwriters of late, part Glen Hansard (Swell Season) and part Richard Thompson, with an Avett Brotherly earnestness and bleeding-poet heart to boot. The hard-strumming, emphatic street-busker sound that defines much of "Sigh" could grow old in a full concert -- and the overblown rock epic "Dust Bowl Bunch" might be best left on record -- but gentler, sweetly harmonized tracks such as "Timshel" should provide a delicate balance.

When's the show? 9 p.m. Tue., Varsity Theater, with the Middle East. Sold out.