Recently I designed an adaptive music system in FMOD Studio that was inspired by a game in development called Perlinoid, which you can check out here.
I recorded a short video to show off the system in action, which you will find below:
In this example the player has control over three primary colours, each of which have their own melodic theme and have been assigned a musical instrument:
Red (R) = Violin Yellow (Y) = Trombone Blue (B) = Clarinet
Depending on which colour the player is controlling the appropriate theme will play. In the background of all this is another short loop that is always playing no matter what happens in game to keep it interesting. To make what I said before possible, I use numbered parameters and sound events to transition between the possible colour combinations. For example the player could be controlling the blue character and then take control of the yellow character, which would be triggered by the parameter B3. From here the player could then go to any of the following:
Y to B Y to R Y to B+R Y to B+Y Y to R+Y Y to B+R+Y
Since the player could make these changes at any given time I had to automated the transitions to fade in and out so they could smoothly transition without bringing too much attention to themselves. Once the adaptive design was ready then I exported the build out of FMOD and into Unity for testing. If you have any questions about this system I created I am more than happy to answer them for you!