It was a couple of years ago for the heck of it I bought a John Williams Greatest Hits collection off Amazon. It covered his most popular movie themes and such from the late 60s-1999 with The Phantom Menace. Which is pretty much his whole career since in the 21st Century I don't think he has done nearly as much, mostly just Spielberg and Lucas movies.
Anyway, it had a lot of really great themes from classic movies: Jaws, Star Wars, Superman, Raiders of the Lost Ark, The Empire Strikes Back, ET, Jurassic Park, etc. And I can't help thinking, geez, how did one guy make just about every great movie theme song for the last 50 years? Yeah, sure there are other good movie theme songs from that time period but Williams is like the New York Yankees of movie composers. Plus there's the Olympics theme song you hear every couple of years for Summer or Winter Games.
Listening to the album a few times I finally got what really makes his themes work: the hook. It's the same thing that separates the Beatles from lesser songwriters. You've got to have a catchy, memorable hook.
The thing about the themes Williams composed for all those movies above is that you can hum or whistle them pretty easily after a couple of listens. That's what allows them to stick in our heads and thus become memorable. Of course you can't hum or whistle the whole thing, but there's always that one part that hooks you.
In the 21st Century Hans Zimmer has pretty much picked up the mantle with Gladiator, the Nolan Batman movies, Inception, Man of Steel, and even The Simpsons Movie. Then there are Zimmer imitators like the guy who did the music for the Transformers movies. Anyway, I own Zimmer's scores to the Batman movies and Man of Steel, but while I like them, they're just something to listen to in the background. I mean I've listened to them probably a hundred times while I'm writing or editing (right now for instance) but if pressed I couldn't hum a single goddamned note. Whereas you ask me to hum Star Wars or Superman and boom, I can do it just like that.
That is the difference. The thing is, as Williams has gotten older, he hasn't really produced at the same level of quality or quantity. Don't get me wrong, I like "Duel of the Fates" from The Phantom Menace, but like a Hans Zimmer score you can't hum or whistle that. Does anyone (except maybe Tony Laplume) remember the scores to the other two prequel movies? I think he did at least some of the Harry Potter ones so maybe there was something from those but having not watched those I wouldn't know.
If you want, you can tie this into writing. I mean there are memorable stories and sentences and then there are those we forget almost the instant we finish reading them. If you're lucky you can craft something memorable, though most of us never will.