MusicSwitcher is a CFG-driven music mod framework for Kerbal Space Program. It is not a standalone music mod; rather, it is meant as a dependency for other modders to make music mods without having to do any programming. As yet, no such music mods exist; if you have an interest in making such a mod, please do! More info on making music mods is in the readme in the download.
There is also a reference implementation available for your perusal.
Raw stats are from the beginning of time until now. Each follower and download entry represents one hour of data. Uneventful hours are omitted.