LIVERPOOL, England — Every so often a band arrives, seemingly from nowhere, out of left field and fully-formed, with a sound, image and narrative so flawlessly off-kilter that once discovered, you wonder how you ever did without them.

Over the last 12 months, The xx have been that band. Unknown by all but the coolest, ear-to-the-ground music aficionados a year ago, a group of unassuming, introverted school friends from South London have, despite having just hit their 20s, created the most soulful, poignant, hauntingly unique album in recent memory, becoming the cult band of choice in the process.

To find them one afternoon in a diminutive, grubby venue in Liverpool feels somehow inherently wrong, and it acts as a real juxtaposition with the splendorous, exalted, spacious music that fills their debut album, "xx."