“Old Town Road” officially became the most popular song in America today. But it’s also the most controversial. Vox’s Allegra Frank chronicles Lil Nas X’s challenges with the charts and Charlie Harding, co-host of the “Switched on Pop” podcast, attempts to figure out what counts as country. (Transcript here.)*An earlier version of our episode misstated the origins of “country trap.” Lil Nas X calls Young Thug a pioneer in the genre.