When the British soul belter Adele began working on the follow-up to her 2008 debut 19, she had a difficult time finding songwriting inspiration. Then, her relationship imploded—and within a day of her breakup, she and producer Paul Epworth had written the stormy, tearful "Rolling in the Deep", which would go on to not only open her second album, 21, but eventually become one of 2011's defining singles and set the tone for a vibrant portrait of young heartbreak that showcases Adele's fierce alto. On 19, Adele established herself as a key part of the 2000s class of British R&B-inspired singers that included Amy Winehouse and Duffy. For 21, however, she added new dimensions to her sound, bringing in ideas borrowed from country, rock, gospel and modern pop—as well as a gently psychedelic take on the downcast "Lovesong", originally by fellow Brit miserablists The Cure. Adele's powerful voice and unguarded feelings were 21's main draw, but her savvy about using them—and only going all in when a song's emotional force required her to do so—made it one of the 21st century's biggest albums. While a few top-tier producers, including Rick Rubin, Ryan Tedder and Dan Wilson, worked on 21, its coherence comes from the woman at its centre, whose voice channels the anguish of the stirring ballad "One and Only", the weepy "Don't You Remember" and the vengeful "Rumour Has It". The stripped-down "Someone Like You", meanwhile, is the natural bookend to "Rolling", its bittersweet lyrics and quietly anguished vocal sounding like the aftermath of the argument that track began. “21 isn't even my record—it belongs to the people,” Adele told Apple Music in 2015. That's true in a sense; 21 was one of the 2010s' true pop successes, reaching listeners from all over the world. But Adele is its key ingredient, a modern soul singer whose range is only matched by her ability to conjure up deeply felt emotions.