Wow, I guess this isn't a very popular command! Either that or people read the documentation and hard-code the AG_PLAYSOUND opcode as 105 rather than using symbol from ashell.def. The AG_PLAYSOUND symbol was added 11 years ago, but was entered incorrectly as having value 104 instead of 105. It should look like this:
define AG_PLAYSOUND = 105 ! [245] Play a sound [311] was 104
(Confusion was introduced by skipping 104, which is actually defined as a function that disable redraw for a control, but apparently was never documented on the theory that it was really only for internal use.)
You can download the corrected ashell.def file from the repository
here.