Back in the 1970’s there was some comedian/musician (Bobby Goldsborough, maybe?) who had a TV show in which he was humorously explaining Pop music. He was saying Pop music has, for eons, been broken down into
[ul]
[li]person A (typically a boy) meets person B (typically a girl) [/li][li]person A pines for person B[/li][li]person A and person B start dating; they’re sooooo in love…[/li][li]person A breaks up with person B[/li][li]person A whines about missing person B[/li][li]person A crows about person B coming back[/li][/ul]
That IS Pop music, whether it’s set to orchestral, folk, latin, jazz, carribean, punk, electronic synthesized, mariachi, thrash-metal, blues, grunge, soul, bluegrass, or polka* instrumentations.
Pop music is characterized by catchy repetitive choruses and frequent airplay, which becomes earworms 
It’s POPular. The target audience is primarily teenagers and young people around 25 and under. Why? Because that age group is heavily concerned with relationships AND because, since the end of WWII, that age group$ has extra money from allowances and/or part-time jobs that they have nothing better to spend on than a personal copy of the latest pop music recording.
The other stuff you list is more like Adult Contemporary music. Young teenagers don’t want to worry about death (after all, they’re invincible!) and, hopefully, aren’t worrying about giving birth# or paying mortgages.
“Pop music often tells you everything is okay, while rock music tells you that it’s not okay, but you can change it.” --Bono (U2)
There are, of course, lots of other genre in music, even in modern music. Some differences have to do with the technical formulas (I, III, V-flat versus I, III, IV, V versus ???) and some have to do with the moods and themes (the world is great versus the world is fine so long as you’re stoned versus disenfranchised anger versus repressed rage versus meditative bliss) being conveyed.
But, aside from existing to be played over and over and over and over and over and over and over and over and over on the radio, Pop music is also an ideal format because the masses who favor it so much are often able, willing, and eager to shell out their money to the advertisers whose commercials are broadcast in between all of those endless repetitions of catchy feel-good tunes.
–G!
- Yes, I’m exaggerating and I know I’ve mixed in styles with formats.
$ Because everyone in that age group is either affluent or inconsequential (yes, I’m stealing this from the late Douglas Adams).
