It would look something like this:

> # cat /etc/system/config/audio/preferences
> pcmPreferredp	"Audiopci 1371"	1
>

Preferred device name (you can set preferred playback or capture 
device), the device name (if you have the audio driver source you can 
lookup the function call to ado_card_set_shortname(); if you don't, you 
should be able to get this by calling snd_pcm_info() and looking at 
snd_pcm_info_t.name (this is the longname, not the shortname, but should 
still work).  The last number is the device number for that card.

With the above config my /dev/snd/ looks like this:
-rw-rw-rw-  1 root      root              0 Jul 28 17:31 pcmC0D0p
-rw-rw-rw-  1 root      root              0 Jul 28 17:31 pcmC0D1p
lrw-rw-rw-  1 root      root              0 Jul 28 17:31 pcmPreferredp 
-> pcmC0D1p

If I swap the last 1 for 0, pcmPreferredp points to pcmC0D0p.

-- 
Ryan J. Allen
QNX Software Systems