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From: trotter@ENUXHA.EAS.ASU.EDU (Russell T. Trotter)
Newsgroups: comp.sys.mac.programmer
Subject: Re: HELP - Asynchronous Sound Manager Calls
Keywords: sound snd
Message-ID: <9102180558.AA13374@enuxha.eas.asu.edu>
Date: 18 Feb 91 05:58:02 GMT
References: <6797@munnari.oz.au>
Sender: daemon@ucbvax.BERKELEY.EDU
Reply-To: trotter@enuxha.eas.asu.edu (Russell T. Trotter)
Organization: Arizona State Univ, Tempe AZ
Lines: 12

I have heard that one should dispose of the channel immediately after
playing the sound (SndPlay call), everything else looks OK!

You may find some help in the Usenet Mac programmers guide, it has
some sample code and stuff specifically for doing async sound. 
Also I recommend getting the latest docs on the Sound manager.
These are availiable from apple.com.  They say that these docs
replace the incorrect and outdated Sound Manager stuff in IM V.
Hope that helps.  

One more thing about your code .  Make sure your callback routine is
doing the "right " thing with A5 and all.