I know I’m always goddess-harping on about Zelda but here is a really good example of dynamic musical layering.
In The Legend of Zelda: Skyward Sword the level design for the third temple centers around a timeshift mechanic where link can hit crystals that shift the immediate vicinity to a time where the Lanayru Mining Facility flourished. In the present time the land is a desert inhabited by crustaceans and the remains of the old mining robots. In the past it was a working industrial facility.
When in the present the music has a much blander texture and is as arid and desolate as the desert for which this music is representing. When link moves into the area that is timeshifted the music takes on a much richer texture gaining new instruments and more details.
Although this is not a new feature it is really done to the highest standard I have yet seen in a videogame.
You can check out the musical differences ingame on any one of the links on this page: