Amos Lee is a 32-year-old soul man with a voice that blends James Taylor and Bill Withers. Lee's singing is both seductive and a little anonymous, his persona often dissolving into a tasteful mix of predictable lyrics and buttery timbres. For that reason, like his labelmate Norah Jones, Lee is a great foil, and the standouts on his chart-topping fourth album — cut with cowboy-mystic indie rockers Calexico providing moody backup — are the cameo tracks. Lucinda Williams is a trembling lover on "Clear Blue Eyes." And on "Behind Me Now/El Camino (Reprise)," Willie Nelson drops in for a duet that's whiskey and cool water: a perfect mix.  

Listen to "Out of the Cold":

Gallery: The 20 Most Memorable Duets of All Time

“Help Me”

Joni Mitchell wrote and recorded this song for her album Court and Spark, but she had to switch from her regular band to make the song sound exactly the way she wanted. "I had attempted to play my music with rock & roll players," she told Rolling Stone. "They’d laugh, 'Awww, isn't that cute? She's trying to teach us how to play.'" Mitchell switched to a jazz band, Tom Scott’s L.A. Express, and scored the biggest hit of her career in the process.