17. Niall Horan, 'Flicker'
One Direction's affable Irishman turns on the soft-rock charm on his solo debut, which, at its most satisfying moments, brings to mind Maroon 5's earlier, funkier days ("On the Loose") and Jason Mraz's semi-unplugged balladry ("This Town," "Fire Away"). Nashville upstart Maren Morris drops by for "Seeing Blind," a duet that updates the Kenny-and-Dolly ideal. And "Slow Hands" – not so secretly one of the best solo singles from a former 1D member to hit radio this year – rides a slick guitar line as it meticulously unspools its tale of seduction, allowing Horan to winkingly flaunt his fully grown status. M.J.