Thierry doesn't seem to be around anymore.  I believe that he did release the Quick BASIC program to decode the sounds, but I can't find it anywhere in the files section here.  However, there is a mention on YouTube of someone who used it to set up an alternate sound EPROM:
http://www.youtube.com/watch v=p8vgDzgI02E

 

Does anyone have his Quick BASIC program

Thanks!
-J. P.