Mailed to me from a posting on comp.sys.next.programmer:


Do the following on the NeXT:

 /usr/bin/sndconvert -r -c 1 -s 8000 -o <toNextSnd>.snd -f 1 <fromSunSnd>.au
 /usr/bin/sndplay foo.snd

and enjoy...
 - LeeN

There is also a file included, au2snd.c, that will convert sound files in
(hopefully) a similar way. This being summer vacation for me, I have not 
tested any of this because the NeXT I'm logged into is currently about 200
miles away. Testing will commence when I return.
  Instructions on how to compile au2snd are included in the opening remarks.
Type 'head au2snd.c' to see them...
                                              Scott/Diode
                                           s-hofmann@uiuc.edu