easiest way is to simply add a symlink to your webroot pointing at your music folder.
Code:
cd /var/lib/apache/webapp/mywebsite
ln -sv /music
and then
http://mywebsite/music will be where your music lives.
of course, the apache user (probably "www-data" if you've got a stock install) will need rx permissions on the music folder and at least r permissions on the music files.