I've been away for a week or so, and have just spotted this thread. At the risk of offending rap fans, I have to point out something.
Rap is basically an expression of the poverty-stricken, gang-ridden, criminally-oriented inner-city ghetto culture. I've actually studied it in some depth, simply because it's the universal "anthem" or "theme" of almost all the criminals I encounter in my line of work as a prison chaplain. They find it deeply meaningful as an expression of how they grew up, the circumstances of their lives "outside", and an expression of their desperation "inside". This does not strike me as being a particularly good recommendation for its musical merits...
I find rap almost impossible to listen to as I would listen to "music". To me, music is something to which I pay attention, trying to understand what the composer/songwriter is trying to convey, identifying the themes (both main and underlying), feeling the mood evoked by the music, etc. It should be obvious (given this approach) that I enjoy classical music. I also enjoy a number of modern rock "composers": Jethro Tull, the Moody Blues, Mike Oldfield - even some Led Zeppelin and some Metallica, who certainly repay careful listening to identify what they're trying to convey. However, all of these individuals and groups are trying to do something musical. Non-musical "rhythmic noise" doesn't interest me, and I can find no worthwhile reason for its existence.
Rap doesn't even begin to approach this level of listening. The tawdry lyrics, distorted voices, thumping beat, and all-around lack of musical quality make it completely unacceptable to me to even call it "music". It's not music at all, in the classical definition of this term. It has no theme, no structure, no development, that would qualify it for this designation.
I'm sorry if this offends those who listen to rap, but you're free to enjoy it, just as I'm free to loathe it.