"Wake Up Everybody" turns back the clock in all the right ways: The lead single from Legend's album with the Roots is a sparkling cover of Harold Melvin and the Blue Notes' 1975 hit. Over string-drenched retro-funk, Legend splashes his ultrawarm croon all over, cool-rocking the pulpit like he owns the church. Guest rapper Common, meanwhile, stays right on message: "Even in this generation livin' through computers/Only love, love, love can reboot us."

“The A Team”

This debut track from the then-20-year-old British singer-songwriter has a dark story behind it. Sheeran says he culls songwriting inspiration from "viewing other people's situations," which, for the heroine in "The A Team," involves drug addiction and prostitution that began as a teen. Sheeran paints the woman's trials with haunting imagery such as "But lately her face seems/Slowly sinking, wasting/Crumbling like pastries." "I did a gig at a homeless shelter, [and the song] is about one of the women there. It's her story," he said.