FinkPish

The reason you are hearing a lot of these scores reworked is that the editors or music editors will temp in score from another film, usually just as a temporary placeholder. Then a condition occurs called "temp love," where the director will fall in love with the temp score, so it is usually left to the composer to recreate as best he can what the director wants (the temp score), hopefully putting enough of his own flavor into the score. Also, if the director already knows what composer he is working with, he will temp in as much music from that composer's past scores as he can, just to make it easier for everyone.

I work as a music editor, and I've seen this on almost everything I've ever worked on.

Drexl

I guess Thomas Newman does the reworking of temp scores a lot. Erin Brockovich and Road to Perdition have some music in the scores that sounds a lot like the score to American Beauty, which is no surprise since Newman did the scores for all of those films. There's also a scene in Finding Nemo which has music that sounds like it was lifted out of The Shawshank Redemption (both of those were Newman scores too). In the case of FN, it could have been a deliberate homage, though, since in the scene

I just saw a TV spot for A Cinderella Story with music lifted from Dave.

karnblack

Yep. You've hit the nail on the head. When I was taking Film Scoring in college that subject was brought up. Most composers dread the temp score and would rather see the picture without sound, but when the director falls in love with a temp score what's a composer to do? If you don't copy the score someone else will, and you'll be out of a job. And yes, it seems like James Horner has a knack for copying himself. Also, the score to Cobb uses a cue from Alien 3 both composed by Elliot Goldenthal. I can only presume that the director fell in love with the cue and the composer said just use it instead of trying to write something to sound like it.

Buckaroo Banzai

The most glaring re-use of a score for me has to be the end of Die Hard:

Spoilers!!!!!

After the blonde guy gets gunned down by Al, the music cue is clearly lifted from ALIENS. Specifically the piece played soon after the colony is destroyed.

Spoilers!!!!!

Horner, Goldsmith, Williams, Silvestri....these guys have many similar sounding scores, I guess you could call it a trademark. Horner is especially bad for butchering his old themes and pasting them back together for "a New Sound".

Ian