You specifically said sound until now, and that makes a big difference.
The stopsound action does not work for music.
My answer above was only when using sound loops, not music.
Use his method for music.
Play a very short clip of silence.
Yes the music loops automatically but that is just it, the music is background music that plays constantly.
So, calling a file of silence like he said to do is the only way to stop the music.
Like this
;Artificial Intelligence Script
;Header
desc = Stop Music In Zone
;Triggers
:state=0,plrwithinzone=1:music=audiobank\music\generic\main.wav,state=1
.