For the musician Artist Server is a way to publicize your music, and interact with those who enjoy it. For the music fan Artist Server is a great way to discover new music and new musicians.
While at the moment most of the music on the server is in the electronic music area (Trance, Trip-Hop, Techno, etc.) it is open to all forms of music. They started out being geared exclusively toward the electronic musician, and changed focus last year.
I have not used the site in the capacity of a musician, but it looks like a good way to promote. If you try it out, or have tried it out by all means comment and let us know how it went for you.