The Boston Calling Music Festival (May 23-25), which has been hinting about a mysterious artist in its lineup, revealed Thursday that the Decemberists have joined the bill. The Portland, Ore.-based indie-rock band hasn’t played a show together since it toured its last album, “The King Is Dead,” in 2011. Frontman Colin Meloy (at right) e-mailed us Wednesday to say he was excited for the May 24 gig. “I come for the oysters, mainly. I do, however, have lots of great memories about playing in the city.” Boston Calling is the band’s only booked festival this year. Meloy admitted that festivals can be unpredictable, but are usually memorable. “You are typically not given a sound check at festivals, which can give a real edge-of-the-knife feel to the set,” said Meloy. “Also, you’re constantly thrown into close proximity with any number of other cool bands. Lends itself to easily comparing hairstyles / beards / deli trays.” The Decemberists are currently working on a new album. Meloy guesses the band will preview some of the new songs for the Boston crowd. A limited amount of Boston Calling single-day tickets go on sale Thursday at noon.