Check out these 2 threads. Somewhere posted there is the pcmplay program and my bootup init. Just make a similar init script and you'll have bootup sounds too.

http://empeg.comms.net/php/showflat.php?Cat=&Board=empeg_general&Number=78613

http://empeg.comms.net/php/showflat.php?Cat=&Board=hackers_prog&Number=74361