I have just tried out the Alien Arena multiplayer game on Ubuntu. Running it with the default settings with my 1 Gigabyte ATI Radeon card and 6 Gigabytes of RAM, this was one enjoyable game. The focus of this shooter is multiplayer online action. Rather like another quality Linux game Corebreach. You can create your own servers and play against people online or join a game that is already running. The online games work very well, I joined an Instagib deathmatch game and it ran very well. I had 254 ping, but I was still able to score a few frags. The netcode is therefore top quality.
So type sudo apt-get install alien-arena and install this quality game. You will love it.
The music files are in ogg format. They may be found in this folder if you want to listen to them with Audacious.