Dave Wirth
What pop music likes it will do over and over again, and sometimes ad nauseam. Often, it's a hook. Sometimes it's a drum fill (See Phil Collins). Sometimes this is a specific chord progression. The chords "D Major" and "A Major" for example are used over and over in pop music. The most famous example would be Tom Petty's Free Fallin' (Heard in shopping malls everywhere... Perhaps the reason why is because the whole video takes place in a shopping mall. Hmmm).
Phrases in pop music are often roundabout things. They are repeated because it's easier for the song to catch the listener when there are repeats. Often, there are four measures to a phrase. Take the Rolling Stones' Dead Flowers. This song's chords are D - A - G - D, and each chord gets a measure. You would think that the D chord at the end of the phrase is just the same thing as the first chord, but it's not this way. If you know this song well, try playing a D - A - G and singing it. It makes for a funny chipmunky rendition on the song.
Further along this query, the amount of repetitions of the chord progression makes is either equal to Four, or is a multiple of it. Take the first verse of Dead Flowers. D - A - G - D gets repeated exactly four times while the lyrics are being sung!
To me, one of the more perplexing things about pop music is how awesome it sounds when someone goes outside of what is expected. Like, what happens when someone creates a progression or series of progressions that repeats more than four times? In the very same song, the Rolling Stones did just that. Even better, it's in the chorus of the song. First, two repetitions of A - A - D - D (each chord gets a measure). Then, three repetitions of G - G - D - D, and finally one time around of D - A - G - D. In short, they made a slightly unpredictable chorus of six phrases, instead of four like in the verse. The result? Dead Flowers sticks out a little bit more from all the other pop music.
Shout out to Gary Sherman for playing me Dead Flowers first. I don't know if I would have discovered it on my own!
