Meghan Trainor ditches doe-eyed doo-wop for fierce, funky, radio-ready pop hits, and proves she’s more than a one-hit wonder. On Thank You, the “All About That Bass” star trades her retro-R&B style for Bruno Mars-esque vocal flexing and hip-hop-level bravado, flaunting her success on “Watch Me Do” (“I’m the–shhh, be quiet, I been on the no-hater diet,”) and sending up sleaze-balls on the power-anthem “NO.” The standout track, a trop-pop smash titled “I Won’t Let You Down,” was written, fittingly, for herself: “I’ve made my mistakes, probably more than I can count,” she sings,” so from this day on, I won’t let you down.”