I'm going to respond to a lot of posts here, but I don't feel like sorting through and quoting everyone. Hope that's OK.
For the benefit of the board, I'd like to remind folk that "classical" (ie concert) music is not a thing of the past. And I'm not talking about FF soundtracks or movie soundtracks either - I'm talking about modern composers, writing music for the sake of music. Look up Kevin Puts, Steve Reich, John Adams, Nicholas Maw...etc. People are doing different sorts of things now, like not writing outside tonal system (which has been going on for a while now, since Stravinsky and before), but it's still there.
Also, it is unfair to lump all modern classical music into the "disharmonious" label. You may be thinking of 60's serialism. Nowadays, the compositional landscape is such that there is no real stigma - you can write anything, as long as it's your music. If people like it, good for you. Comparing common practice music to hip-hop and pop is a little unfair - there's hardly ever anything harmonically interesting going on in pop or hip-hop - they are written more so people can dance to them and be entertained. Most pop songs on the radio these days, and most days, use 3 chords. That's so if they ever, at one point in the song, use a different chord, it sounds exciting. Indie musicians tend to be a little more adventurous in the music they write, since they don't have multi-billion dollar labels telling them what to do. However, hip-hop still has quite a bit to offer rhythmically, and I can think of several modern composers who admit to drawing rhythmic influence from rap.
In general, modern composers of concert music are trying to do what every great composer throughout history has done - write something new. It's tricky, because so much excellent stuff has been done. Stravinsky was a revolutionary composer because he wrote in a pandiatonic system that his audience had never really heard before. Chopin mixed up traditional progressions using the iii chord as a lead to the dominant - something unique that makes his music sound definitively Chopin-esqe.
(Oh, and the Russian Five wouldn't be writing 2 chord country songs. That's silly. They're better than that. Not that the measure of a piece is determined by how many chords it uses, but there's value in being at least musically interesting.)
OK, sorry about that. You might ask, "goodness, WindFish, why are you such a prick?" Well, I'm a music composition major, working on a string quartet at the moment. Feel free to yell at me or something now.
