You don't learn anything from step by step advices. Step by step advices
create stupid users. You just have to read through the fine
documentation.
/dev/audio can only be opened by one application at a time, in your case
you want aucat to open it so that it can multiplex stuff for you.
If aucat says "Device busy" then that means that another application is
currently using the audio device, kill that application. After you did
that you just have to run "aucat -l" and you're good to go, play your
music in mplayer, vlc, totem, whatever, you will be fine.
Best regards,
Jona
--
Worse is better
Richard P. Gabriel