Regarding what somebody said about Music "replacing" natural lagnuage, I do not think this is the case. Granted, do not get me wrong, I too am enamoured with music and it how it continually presents inner experience and certain aspects of ineffable subjective experience afresh, but It will stay in its domain, I believe. Music, is interesting when thought about as a language or more broadly a means of communication (which it is) because you can see how perceptions of music are culturally related. Just as thought and language co-evolve in an individual in tangent with a culture, so too does music. Of course, just as with any system of communication that has cultural influence, it is possible (and advisable) to transcend your local culture and expand your notions of the system of communication, but many times people do not. I see this all of the time, especially with mass culture music and dance-hip-hop. People are just stuck in that one cultural idiom and what it communicates, they don't "get" other types of musical communication that may be stating something "deeper" more personal or otherwise, but just as with somebody of the mass reading something intelligent or telling, they either do not get it, or claim they do and miss the point.
Of course I can't go into what constitues music 100% because music or the philosophy thereof is a part of aesthetics, a notoriously difficult and abstract branch of philosophy to "Reason" about. My understanding of music is inherently related to aesthetics, a person's message, the originality of expression, and the ways a feeling is being communicated.
I also wish to say that many times people get down on rap as being "insufferable" or "not music" it is a great means of expressing woes, when done properly. MAny people here popular club tunes and rap that is on the radio and deem it all some "bitches and hoes, money, drugs" glorification, which is not the case. Intelligent rappers will talk about these things, being that they are an aspect of the culture, but in a much different light. There are many rappers and rap groups with outright talent. Blackstar (somebody go listen to Thieves in the night and tell me that is not some real stuff lyrically) Talib Kweli, The Roots, some Mos Def, there are many more I just either don' tknow or canot list.
*Oh yea I looked up and saw the "vibrations in mathematical ratios" or whatever and it reminded me of Iannis Xenakis, a composer who organized tones in terms of sets and relations and performed "logical" operations upon the tone rows he organized into classes and made compositions using this technique. He also utilized group theory, the statisical theory of gases and a whole slew of other techniques*