Would an alien race, with a completely different understanding of the world and different values, rate our art and music the same? (Assuming they could comprehend it.) I don't think that they would. Would this call into question the objectivity of artistic value?

I agree that an alien race that differed considerably from us would be unlikely to rate our art and music the same. However, this does not, by itself, show that there is no objectivity in artistic value. If one wished to defend the objectivity of artistic value in the face of such evidence, one might use one of two strategies. (I) One might argue that the alien race is simply mistaken in its value judgements; for some reason---which one would have to independently specify---the aliens get it wrong while we get it right (or vice versa). Alternatively, (II) one might argue for the conditional claim that if the alien race truly understood our art and music, then they would appreciate it; evidence that they do not appreciate should be interpreted as evidence that they do not understand it. Again, one would have to independently specify some reason why the aliens do not understand our art and music. Without more detail on the aliens and their disagreement with us, it is difficult to say which, if either...