It is true that when people say "music is a universal language", they often mean something that is not quite true. It is normally intended that because music doesn't carry information, it can be understood and appreciated by anyone from any culture. Well, that's not strictly true - there are learning barriers, as evidenced by the point about Western listeners understanding Gamelan and vice-versa, they are just more subtle and more easily overcome. It is only the things that we do not have to learn that count as universals, and it is not a piece of music or a musical system that will be a universal, but an underlying neurological capacity for understanding and appreciating pitch (for example).
Again, I have to ask you, if you're trying to suggest that universals don't exist, then explain how language exists at all. The only other explanation that has been proposed is the one of the blank slate - that a mind is utterly bare, and can be shaped in any way by any thing. That has been thoroughly debunked, demonstrating that children are born with innate capabilities, and these capabilities affect emergent culture.
Once again, you fail to offer a replacement. You say science can't do this, or this, or this - well what is doing it then?!