I just downloaded scummvm and am anxious to play zak. It's the FM-towns version(english) and it plays like a dream except there is no sound. I checked the compatibility and it says it's completely compatible. I tried every different sound option in scummvm and still nothing. the FAQ mentions a -s on the command line but I'm still not sure where that is suppose to do.
You need to have your CD inserted while playing so that ScummVM can playback the sound tracks. Or you rip them and place them on your HD (as detailed in the README).
to be fair, I get the impression that forum search sometimes comes up with totally unrelated posts myself... like finding posts where the search term doesn't appear