Minneapolis-based Carroll, one of the most colorful, carefully honed acts in indie rock, are many things: young, vibrant, contemplative. But perhaps most interestingly, they’re a case study in how four distinct creative voices can coalesce into one balanced, relentlessly engaging sound. The mechanics were simple enough: Near the end of 2011, Brian Hurlow’s demos (think melancholic, synth-based pop) caught the ear of his college classmate, Charlie Rudoy. The latter was a drummer who could bring to the songs a live, artful element. The pair quickly moved in together on St. Paul’s Carroll Avenue, tucked neatly in between Summit Hill and the Mississippi River.