At 34, John Legend has sold millions of records, won nine Grammys, collaborated with many of the biggest stars in music (Jay-Z, Kanye West, Alicia Keys, The Roots, et al), and achieved the kind of statesmanlike musical-ambassador status usually afforded to artists twice his age. He is, in short, the sort of star who doesn't usually perform behind desks in offices.

But once we'd wedged a piano back there, Legend sounded perfectly at home. His rich, soulful voice never suffered for a lack of processing and production as he performed three songs for NPR Music and a few hundred of our rapt coworkers, loved ones and hangers-on...