I believe this is because you are checking for the presence of the Space Age DLC using mods['spaceage'] but the mod is named 'space-age'

I was able to fix this by updating line 1 of data.lua to read:

if mods['space-age'] then

Yeah, I goofed up a bit with this typo 'cause I didn't test this mod on other planets except Nauvis...

Anyway, I've updated the mod, thank you very much for your fix - I would have spend a lot of time searching the issue =]

No worries at all, happy to help. Thanks for good tunes! Will keep my eyes out for perhaps a full-blown music player mod from you someday? 😉