Adele Adkins’ debut album, 19, opened with the mellow, twangy ballad “Daydreamer,” but 21 comes out swaggering with “Rolling In The Deep,” a gospel-infused deep-soul number that builds to a soaring disco chorus. Adele follows that immediately with the overpowering “Rumour Has It,” a soul-strutter with a persuasive backbeat, and only then does she settle back into slower-paced, piano-and-acoustic-guitar-driven songs more like her hits from 19. But 21’s initial fire never dims. In the tradition of Dusty Springfield—another Brit with a jones for American R&B—Adele sings spirited songs of heartache, primarily directed toward an ex-lover whom she alternately scorns, begs, and makes desperate promises to. Like Springfield, Adele is also something of a classicist where pop is concerned. 21 sounds mainstream, but never too slick or overloaded. The songs hold to simple instrumentation and simple structures that allow Adele’s raspy, expressive voice to develop the story in the verses before she delivers the hook. The album weaves between danceable and melancholy, with no song coming off as trifling or disposable (aside from the Latin-tinged, cabaret-style acoustic cover of The Cure’s “Lovesong”). When Adele reaches the bridge of the churchy “One And Only,” and sings “I know it ain’t easy” over and over, she sounds credible, even though she’s barely old enough to know whereof she sings.