I have an idea to connect wave music with boss music, something like on a video below. Transition could be with every music, not only CIU ambient and intense theme.
But about in-game music I don’t like 1 thing. If you set certain music in mission configuration, it will always be that one. IA can add more music slots (maybe purchased in store) and music will be randomly picked from one set songs.
I meant it but as an addition to main idea which is music switching. Except fading out wave music and then fading in in boss music, it could be smooth. And if you have equipped CIU ambient theme as a wave music and CIU intense theme as boss music, it won’t start from beginning but in moment, where wave music was. If someone didn’t understand because of my bad english, just check the link.