This is an idea which has made me go "hmmm" more than once.
Let's assume there is life on other planets. Let's also assume that they have auditory abilities. Would there be music? What would it sound like? Would their evolution of music be similar to ours--starting simply, as in chant, developing into polyphony, counterpoint, and so on?
This raises a second question: is the development of music necessarily dependent on the presence of a society? If art imitates life, I suppose that some kind of organized group would be required, or there would be nothing to imitate.
Think about rock'n'roll for example. On another planet, in another galaxy, could there be rock'n'roll? Sure, there could be, but do you suppose it evolved like it did on Earth? What is Planet X's equivalent of Elvis Presley, the Beatles, Grateful Dead, etc.?
Conversely, how different would music be today had certain individuals not existed? Would there be fugues without Bach? Bebop without Charlie Parker?
And the future: do you ever wonder what music will be like in the future? Is it possible that every conceivable combination of tones has been used at least once, and now all music is recycled, regurgitated, redone? This really makes me go "hmm." We can't predict how music will evolve (we linear-minded humans).
I'm scared about the future of music. Pop music today sounds as recycled as the styles in Old Navy. They've matched up Jackson 5 tunes and belt-buckle jeans with Britney Spears and belt-buckle jeans. SOS (same old shit, as Jimi would say). It's maddening.
I think this is why I like Star Trek Voyager. In the 24th century, humans are in contact with species from planets all around the universe. I wish I could beam myself into the future, or be part of some spacial anomaly, so I could study the music of a different planet. I'm getting bored with Earth!