David Letterman obviously likes what Simpson is doing, too. He had the country artist back on The Late Show last Thursday night (Feb. 11), where he performed "Long White Line."

Traditional country music fans were immediately drawn to his record, with his voice being compared to Waylon Jennings. But his lyrics were pretty, well, 'metamodern'-in other words, different than most other songs in country, or any other genre, for that matter.

When we profiled Simpson for our New Music To Know series, he told us he wasn't quite sure he lived up to the hype of the critical acclaim he was getting. "A lot of people have said it's progressive and groundbreaking-I didn't think it was that progressive," he said of the beloved opening track, "Turtles All The Way Down."