Beauty is completely in the eyes (and the ears in this occassion) of the beholder.
I see a struggle of everyone to prove if this 20th century music has musical value or not, regardless of difficulty. Any piece of music doesn't in any case need to be necessarily difficult or easy to be beautiful, or total nonsense.
I started taking piano lessons when I was little for one reason only: because Chopin's 3rd Sonata (my uncle's "accident" Xmas gift) brought feelings of great variety to me. I wonder what would have happened if I was listening to Finnissy or Xenakis back then...I would most probably never had learned music at all. So, if such a complicated piece of music (Chopin) can attract a 10-year-old this way, I rest my case for its musical value.
Just because music is supposed to provoke emotions (this is the reason arts exist eitherway), I am very curious to know what Xenakis - Finnissy - Younametherest listeners feel or think when they listen to this kind of random (because random it sounds) "music", and equally important, how often you listen to it. Despite I might get shot at spot here, I really doubt the musical value of this "stuff", strictly personal opinion. It shows nothing but this mule wave of "art" that has filled ALL kinds of contemporary artistic valor with absence of what art as a means of appealing the senses is all about. It is one thing to try to be artistically different, and another to underestimate people's intelligence.
An extreme example - parallelism of our subject: Michaelangelo's "Pieta". Art of sculpture at its finest, no need to debate on that. Now a 20th century neo-sculptor "artist" comes to me with a piece of interconnected spark plugs, pieces of wood, springs and the head of a doll, gives it a flashy, irrelevant name, and calls it art. And sells it 80000$ just because his name is "Huberstauffertulungen the 2nd". Give me a break weirdo. Put this in your own living room. And the saddest of all: There WILL be people who will buy it because of its artistic value, and not as a means to invest their money.
I for one would prefer to listen to Britney Spears and give my ears a rest.

Or plug my midi keyboard and start banging it with 3 baseball bats...I might come up with an interesting score!