Hank Williams wrote so many classics that it's hard to single one out that's better than the next, but "I'm So Lonesome I Could Cry" holds a special place in his catalog. A mournful tale of loneliness, the song contains some of the most evocative lines Williams ever wrote: The opening couplet of "Hear that lonesome whippoorwill/He sounds too blue to fly" is a model of simple, elegant poetry. He married the lyric to a melody that is equally simple and graceful, resulting in the kind of song that sounds like it was never written -- it was just always there. That quality is the reason why the song has been performed by all kinds of musicians, each shaping the song in their own style and often delivering a unique interpretation. Even within the scope of country music, there are a number of unique readings -- Willie Nelson, Johnny Cash, Marty Robbins, and Charlie Rich's versions have different emotional tones -- but Al Green's soulful interpretation was moving, as was Cassandra Wilson's jazzy take. Williams pulled off a neat trick writing a song that's undeniably personal, yet universal enough to make it convincing -- even personal -- in the hands of other musicians.