In at least the most recent version of RND: While trying to play at least a few levelsets that from what I remember shouldn't have music (as their musicinfo.conf files are normally set specifically to prevent music from playing by setting everything to "[NONE]), I noticed a few oddities with the music when playing. So I checked the Setup menu for any overrides, and checked the levelsets' musicinfo.conf files for probable typos that may have not existed before. I don't see anything wrong, but what I did take note of in this oddity made me notice I likely found an error in the engine:
The game seems to completely ignore the command to play "[NONE]" for playing music in levels, as despite "background.LEVELS" in the musicinfo.conf being set to "[NONE]" it continues to play all of RND's default background music in levels. As an indirect result, "rhythmloop.wav" also plays during levels due to "background.INFO" in the musicinfo.conf being set to not play "rhythmloop.wav".
Oddity in music behavior
Moderators: Flumminator, Zomis
Re: Oddity in music behavior
There is indeed a bug in the latest version 4.3.6.0 that causes the described behaviour. 
It's most noticeable when playing any level from the "Emerald Mine Club" level collection, which is configured not to have in-game music, but instead plays the "default" in-game music tracks.
I have already fixed this bug in my working version, which will either be released with the upcoming version 4.3.7.0 or with a dedicated bugfix release.
Thanks for reporting this bug!
It's most noticeable when playing any level from the "Emerald Mine Club" level collection, which is configured not to have in-game music, but instead plays the "default" in-game music tracks.
I have already fixed this bug in my working version, which will either be released with the upcoming version 4.3.7.0 or with a dedicated bugfix release.
Thanks for reporting this bug!