The problem with terms like these is the music at the boundaries. There's pop and jazz music that sound more like art than some concert music. There's art music that will never see the inside of a concert hall. What about interactive computer music? Is it art? Is it a game? Is it theater? Is it improv? What about music that arises out of dance movement? Is it dance music?
What's "serious"? What's a "composer"? What's "art"? What's "sound"? And just like any jargon, it depends on the audience with which you're communicating. The more you try to standardize a definition, the more star systems will slip through your fingers.
Yes. It's utterly pointless to set these distinctions. Iggy and the Stooges and the Ramones were disciplined conceptual artists, yet they were part of a movement that spelled stupid "stoopid". The beautiful thing about real art, the kind that gets remembered as great art later, is that it is always ahead of the theoretical game.
A famous example is Shakespeare, who was vulgar until the German Romantics discovered him as classic.
What's "serious"? What's a "composer"? What's "art"? What's "sound"? And just like any jargon, it depends on the audience with which you're communicating. The more you try to standardize a definition, the more star systems will slip through your fingers.