just to jump in ......on gentoo, you already have an audio group. you may need to edit /etc/group and add your name to the group.
also, if you are not up and running...make sure you do:
emerge alsa-oss
and
modprobe snd-pcm-oss
you should then see 'snd-pcm-oss' along with your other alsa modules when you do lsmod
here is a good guide on how to set up the alsa modules on gentoo:
http://www.gentoo.org/doc/en/alsa-guide.xml
-august.