After a very long, very cryptic teaser campaign, Boards of Canada are officially back—sort of. A mysterious, three-minute piece of music, titled “Tape 5,” appeared on the Scottish duo’s YouTube this morning, with corresponding uploads on the social channels of their longtime label Warp . No information—or even formal confirmation that it is new BoC music—is at hand, however. Listen to “Tape 5” and decide for yourself below. Boards of Canada’s outsize influence, psychedelic sound palette, and sideways worldview never went away. In a very real sense, however, Boards of Canada did go away—for 13 years. Since their fourth album, 2013’s Tomorrow’s Harvest , intermittent signs of life have appeared in the form of seemingly random remixes , archival reissues , and an NTS DJ mix . True to form, the Boards of Canada resurrection has murmured to life so quietly that only the most obsessive of code breakers twigged it early on.…