Years ago (and for 12 years), I worked as the classical music director for a college radio station. My job was to program the classical music, which ran from 8 to 12 every morning, and to teach novice students (who often didn't have the least bit of interest in classical music, but wanted to be on the radio) how to speak properly, pronounce "foreign" names properly, how to flip records (yes, we used turntables back then), and to begin to understand something about the music that they were playing.
I remember one of my students saying something like, "Some of this music actually has a beat to it." I was puzzled by her comment. Of course music has a "beat" to it. That's what I call rhythm and/or meter. But I came to understand that "beat" means something different in pop music from what it means in music of the "non-pop." (Insert your own Clemens-non-papa joke here.) I realized that conforming to a established "beat" is one of the essential elements involved in writing successful 21st-century pop music.
The pop song When You Make Love To Me (Don't Make Believe) that Jascha Heifetz wrote under the pseudonym of Jim Hoyl, is an appropriate mixture of Jerome Kern and George Gershwin. There's nothing in it that sounds truly original, but something that is too original can never be an instant hit. The melodic and harmonic material of a successful pop song is already familiar the first time you hear it. It's like a cupcake. It's small, predictable in form, and calls attention to itself by its decoration (its lyrics), and perhaps a bit of surprise filling inside (which is also usually made of a rich and recognizable substance).
The performance of a pop song is tremendously important. All forms (or "covers") of Ben Folds' "The Luckiest" pale in comparison to his performance. If Bing Crosby hadn't recorded "Jim Hoyl's" song, it might have never become a hit (the Crosby recording is unfortunately not available on YouTube). Pop songs are almost always connected with a performer. In the case of Folds, the performer is the composer.
I got on this ramble after listening to a podcast on "The Story"," about a project called Eight in Eight where Folds, Amanda Palmer, Neil Gaman, and Damian Kulash set out to write and record eight songs in eight hours (they completed six songs in twelve hours). They wrote the lyrics for the songs with the help of their fans, who gave them ideas by way of twitter, but their clever lyricist did most of the actual writing work. The result is a bunch of songs with clever lyrics and melodies and harmonic progressions that I would consider (I didn't hear everything--only what was in the podcast) mainly derivative. Without the words I doubt I would be able to identify the music I heard as anything different from the scores of well-put-together pop songs (and I suppose I mean "indie" pop songs) from the first decade of the 21st century and the last years of the 20th. Still, these people are good musicians, and they have succeeded in doing what they set out to do.
I suppose that one difference between contemporary "pop" music and contemporary "classical" music, is that "classical" composers try to make music that is original from a melodic or harmonic perspective. Originality, when it comes to music, is, of course, a near impossibility, but "classical" composers fight the urge to do something that has been done before (at least I do), and pop music composers seem to embrace established traditions and flex their creative muscles by dressing their music up with their own "twists" (or decking them with attractive lyrical "frosting"). Originality in pop music does pop up now and again, but it doesn't seem to be the "rule." And there are also not-necessarily-original pop songs that I would consider excellent music.
Before there was pop music as we know it, what we call "classical" music followed formulas of the day. There are countless pieces of Renaissance "wallpaper" music that you have to wade through in order to get to something truly original (but it's always worth the wade). It's the same with Baroque music, only more so, because more of it was published. Originality in the Classical Period was proportionally scarce. Haydn and Mozart couldn't help being original, but perhaps their music was embraced by the larger world because of its quality, and not because of its originality. Perhaps it was with Beethoven and then with the rise of music criticism that originality began to be prized in "intellectual" circles. Some people "got" late Beethoven, and some people didn't.
This is just a ramble, and I'm sure I'm not saying anything new, so I'll stop now.