What we recognize as "Music
" is simply what we're taught to recognize as music.
The argument by enth poses interesting questions about changing musical perception through time. I disagree with the main point that there is some unchangable element in our cultural training that makes something "sound like music" and something else "not sound like music". From the time we are born, we are sung to in a certain temperment, we hear the rhythms of the language which our parents speak, and we hear music in many shared cultural environments. All the while, we are being told what is and what is not music.
With that in mind, I also acknowledge that what one thinks of as music can change as one's perceptions and/or environment changes. For example, since I've begun to study experimental music, my own personal conception of "music" has radically expanded, indeed to include enth's example of "twenty-four hour long masterpieces that if listened to by us would sound like endless, droning chords and buzzes" (see La Monte Young).
There is music being made right now that most people in the world would not recognize as music even though it is being made at the same time in which they are living. One of the true marks of our so-called postmodern time, is the irrelevance of the concepts of "past" and "future", and the expansion of the present to include all that has happened and all that will happen. For example, because live music has been reduced to the position of novelty in our present culture, recorded music has come to represent music for most people. However, recordings of music from every culture and time up to the present are available with a few mouse clicks, and an hour's or two wages. Can there truly be a singular musical perception of our time when one can easily hear blues, rock, gamelan, gagaku, estampie, chant at any time they please?
Of course, in every time and every culture, there exist those who believe in the dogma of a singular true music. To these people, any music outside their normal experience is not music, and there is no way anyone can change their opinions. That is true for some insular feudal lord only listening to sacred chant, and for some closed-minded conservatory teacher, only listening to 19th century classical music.