worldbuilding thought
thinking of what music by alien species would be like and honestly, I figure the main differences from what you find here on Earth would be more in the rhythmical and instrumentation (or if electronic, sound design) department than harmony per se
there's only so many combinations of chords you can smash together that'll sound right even if you consider differences in the theory behind it all and plenty of music here on Earth doesn't use chords, period
worldbuilding thought
i mean sure there's microtonal stuff & all, & to expect everything made by people elsewhere in the universe would be in 12TET would be a joke, but no matter how many keys you add to the keyboard, there's only gonna be so many combinations of intervals that sound nice together
of course which ones prove the most popular and for what is a whole other thing, but given how much the 7½ billion of us have collectively messed with that ourselves, probably nothing new under the sun