"Mammas Don't Let Your Babies Grow Up to Be Cowboys" (1979)
For all the hit songs that Nelson wrote for other people over the years, it's hard to think of a song written by someone else that could be as perfectly suited for him as "Mammas Don't Let Your Babies Grow Up to Be Cowboys." The song had already charted with its author, Ed Bruce, and been covered by Chris LeDoux before Nelson and Waylon Jennings tackled it on 1978's Waylon & Willie – but all other versions were relegated to footnotes once they'd touched it. (Even the Chipmunks', whose parody was inspired by Nelson and Jennings' definitive reading.) The Lone Star belt buckles and smoky old pool rooms fit in perfectly with the outlaw country mystique, but it’s the delivery that sells it: You get the feeling that Jennings is that dark, distant cowboy, but Nelson's warm, airy contrast gives the song the wry, knowing wink that it needs.