Even though Okkervil River mastermind Will Sheff can be playful and humorous in the live setting, his music still has a penchant for being quite downtrodden. Two of his newest cuts – including “Wake & Be Fine”, which he debuted alongside A.C Newman and The Roots on Late Night With Jimmy Fallon – feature the dark, introspective lyrics he’s come to known for, and the Austin-Tex.-based outfit’s newest single is no different.

Pitchfork has turned us on to a B-side from Okkervil River’s upcoming album – I Am Very Far – and if “Mermaids” is any indication of what’s to come, then we might be looking at one of 2011’s best releases finally arriving on May 10th. The five-minute cut is a swooning, instrumentally lush lament on the mythical sea creature that deals with separation and loss in a way that Sheff has come to be very good at.

Swirling strings, triumphant horns, and big pianos are all mixed with great results, which Sheff said required I Am Very Far’s personnel to be right on point all the time. “Everyone felt this immense amount of pressure,” he said of a particular recording session that put 13 people in the room at the same time, “We all had to give the best performance of our lives for this to work – if any one person made a mistake, they would ruin the whole song.”

Sheff (who says the interview process of album promotion reminds him of autopsies that make his past records look like “piles of guts” to him) doesn’t provide many more details, opting instead to preserve the “mystery between the title and the music,” but at least you can ponder that mystery by streaming “Mermaids” here.

If you like what you hear, head over to Jagjaguwar to cop the single, which also includes another B-side (“Walked Out On A Line”) today.