Theme evolution -- how common?

I'm playing through Persona 3 and I've noticed the Tartarus theme 'opens up' as you progress through the game, adding layers of complexity,  similar to the way the Comet Observatory theme worked in Super Mario Galaxy. I think this is an interesting way to reward players, and reinforce the idea that progression is occurring. These are the only two games that come to mind. Anyone know of others?
 
I think the key points of this concept are evolution, not radical variation, based on progression and having some element of centrality or ubiquity in the game.