I guess there are all kind of structures and "rules" in there but it's from a different culture to the one I grew up in so I don't have an in-built frame of reference. I'm not trying to play the tired old game of "the mysteries of the east" as if it's only the non-western world which is so enigmatic. To people raised in that culture the one I live in must look equally strange. Some days it puzzles me at the moment - but I'm going to stop that thought there as this could descent into a political rant.
I got into this kind of thing after taking a punt on some gamelan music in a record store. Sometimes it seems the only way to find something new and interesting these days: just pick something up at random or on the basis of a name or an interesting image on the cover. With the way music seems to be codified into innumerable genres these days, leaping randomly across the categories ends up being the only way to avoid the mechanical recommendation process where some algorithm has been compiled on the assumption that people only like music which is the same as everything else they like.
I've never been anywhere near Indonesia and probably never will. I have no clue about any cultural significance attached to any of this music. My appreciation of it is purely aesthetic.
In short, it's lovely and I'm happy to say I don't know why.