Think of pop music as being like the parable of the sower. These days the seed falling on stony ground comes from the young rock bands, while the stuff that’s finding fertile earth is on the edges of R&B where it shades into other styles, especially psychedelia. It works from both ends: the Australian group Tame Impala went from being a workaday psychedelic rock band to being festival headliners by bringing dance music into their sound.