I've just made a purevolume site to post my originals on, but when I try streaming from the site, the cymbals for the drums sound distorted and the quality is low. But, one of my songs is coming through with good cymbal crashes and good quality, the one titled "Evil".

Does anyone know why this is happening?

Here, check these out and you'll see what I mean. http://www.purevolume.com/nottobetakenseriously
Purevolume compresses the files further to save bandwidth (which is what all hosting companies really charge for, space isn't an issue, hard drives are super cheap compared to prices of bandwith). To compress the files the encoder filters through the song and removes parts that it "thinks" the typical listener can afford to miss. In most cases, the high frequencies. To compensate for that, you can boost the high frequencies and save a new file specially made for purevolume. When purevolume filters out some of those frequencies, it'll sound a little more normal =)
Quote by les_paul_01
In Soviet Russia, song copyrights you!