Hi Mitchell,
There's a couple of ways to do this. One would be to use the DontDestroyOnLoad() function on the object you posted your music on.
Another one could be to have a separate scene that is always maintained. For instance, you could have a "Main" Scene that keeps track of e.g. process stats. If that scene is always loaded, then that would be great for playing music across scenes loaded additively.
Let us know if you get it to work!