Zach Crowell thrives creatively when he’s bouncing sounds and ideas off of other musicians, including longtime collaborator Sam Hunt. But because the Nashville native is also a studio jack-of-all-trades, he brings a producer’s keen ear for detail to his country co-writes. His yearning acoustic-guitar licks add bite to Kelsea Ballerini’s “Roses,” while sleek programming on Carrie Underwood’s lovelorn ballad “Heartbeat” adds a pleasing pop sheen.