I definitely share the passion (of talking 'bout great music, I mean) with you, Nick.
Oh, I'm sixteen, by the way, since you were curious.
The change of tone thing is something I've always wanted to bring up but never thought anyone would get. In case you hadn't guessed, I'm not so fond of contemporary artists (especially not female singer-songwriters) and I've noticed the artificiality of the singing. It's always ultra-soft to accent a non-existent sincerity, or with the more banal little screaming brats (Pink/Kelly Osbourne) un-melodic shouting is used to give the impression of being strong minded or rebellious or whatever, when in both cases there's no real message - just an image. Hey, Joni Mitchell and bob Dylan never had to half-sing/half-sob to make me cry...
I think you're very right about music being an emotional tool... I do belive it's the best method (or at least most direct) of communication of feelings. It's a curious thing, noting that, to realize that music is also the most physical expressive artform: Painting, poetry, and scultping all involve a lot less use of the body.
But it's also a very important journalistic/intellectual tool because it can say what the media can't. That's something today's crooners seem to have sadly forgotten, but the Airplane is actually a great example of the socio-political angle. Rejoyce is probably as good an attack on suburbanite conservative middle-class culture as any 40 page essay, and let's not even start on Paul's social commentary...
"War's good business, so give your sons
But I'd rather have my country die for me" ~ Grace Slick, Rejoyce 1967