You can give music types a higher priority than 1

[Selene310187]

TL;DR: The highest priority of a Music Type is surprisingly 0.

I experimented a lot with the implementation of custom music, which is added via the add() command, during the development of my Spectral Music Player mod. Recently, I wanted that the playback of the custom music won't get interrupted by any default music of the game. So I set the priority of the custom music types to 1 but this conflicted with the special music (like level up music) which also has a priority of 1. I believed that giving the special music a priority of 0 would prevent the special music from playing when the situation requests it. The effect was quite the opposite - the special music always played. I removed the changes from the special music and gave the custom music types a priority of 0 instead. When my character made a level up, the playback of the custom music was finally no longer interrupted by the level up music.