Pop music hits on the generations has changed immensely with no more so in comparison to the last 5 years. Throughout the evolution of popular music before the last Two decades pop music usually encompassed only one genre of music. Take into account Baroque, Renaissance, and Classical music. The music was by different composers but stayed well within the same kind of musical category. When recorded music came on the scene and started being broadcasted over radio waves the transmission of pop music hits became different but not it overall mandate that was that it still retained its origin in a type of music.
Think about the advent of jazz noisy . part of the Last century. Jazz was prevalent for a while as the main type of pop music. Whatever you heard might have a jazz feel into it. We're talking pop jazz here not the blues, the blues although popular amongst musicians themselves were really an influential genre when compared to a popular one. Then obviously there was rock and roll which really dominated the pop music hit culture before advent of Motown and R&B music.
Stone and R&B dominated pop music until Disco emerged and then to some small extent country music gained some popularity being a main stream genre. The 70's was obviously a mixed bag of rock, R&B, ballads and new bands, mixed in after a little kitsch. Remember, CW McCall? Rock and R&B still dominated though showing its resilience right until the late 1980's when Rap came onto the scene. This mixture of pop music hits began to change a bit. Rock and roll had been knocked out a bit by Rap and R&B and it was no longer the dominant force in pop.
Today, pop music hits is now an amalgamation of all of the music genres. You will have a country song, R&B song, and Rap songs all on a single pop chart. Indeed, even r / c have changed around their formats being more ubiquitous and less focused on just one kind of music. The influences are typical still there because of rock and roll but the cadence and tunes themselves have changed and transmogrified in to the mix of songwriter we have adopted within the last five years. Like everything pop music has progressed and expanded exponentially nowadays most of which has occurred just within the last five years.