Rock music is far from the center of the pop music zeitgeist in 2018, but it’s possible that the state of pop music — or at least, the industry of pop music — demands rock stars, and even rock “bands,” while not worrying much about whether the music slotted into those categories would be recognizable as rock to fans of one or two generations ago.

This theory is borne out by the success of acts like Twenty One Pilots and the 1975, which are, broadly speaking, advertised as rock bands, and whose music appears on the Billboard rock charts, but whose albums are widely diverse, taking in electronic music, R&B, hip-hop and reggae. And it is supported by the unlikely rise of Greta Van Fleet, the exception that proves the rule: a band that closely traces Led Zeppelin and seemingly exists only as an answer to cries that no true rock bands exist anymore.

Is rock a sound, or a mood or a retail category? What will it take for mainstream rock to be something other than the preserve of white men? Why are the Billboard rock charts so erratic, lumping together acts with very little in common?

On this week’s Popcast: