After 27 years in print as 24 Greatest Hits, Mercury kindly reduced it to 20 Greatest Hits. It's still excellent value, and it's still sobering to realize that Hank recorded just 66 songs during his lifetime, almost all of them essential. Here are those that serve as a working definition of country music, and as an admonition to artists who try to get too wordy or try to lose themselves in minor keys. "Your Cheatin' Heart," "Honky-Tonk Blues," "Cold,...