A month after ABBA rose from the glittery pop ashes and released, frankly, two underwhelming comeback singles that didn’t sound much like them, our patience has been rewarded with a travel back in time: The Swedish legends unveiled their newest track “Just a Notion,” a ridiculously happy romp that finds Agnetha, Björn, Benny, and Anni-Frid harmonizing about the joys of flirting while a power piano noodles in the background. (A top ABBA sonic theme, after battle metaphors for romance.) The song was originally recorded in late 1978 for the group’s Voulez-Vous sessions but was left on the cutting room floor for reasons that remain elusive. “Why did we decide against it? In hindsight, I don’t have a clue,” Björn explained in a statement. “So it’s a mystery and will remain a mystery.” We have it on loop.