By chance, the first time I tried GK, the SFX worked,
but not the speech.
I had copied the GK CD onto the DOSBOX directory.
Then, I mounted the CD in DOSBox and installed
the program and then I had the same problem as you,
the error
Checking what were the differences, I found that
the first time, the Install program created a
different resource cfg, with more options,
but missing the folders part.
So I merged both resource.cfgs, and now it works
for me: audio, speech and MIDI 😁
This is my resource.cfg
====
videoDrv = VGA.DRV
soundDrv = MT32.DRV
audioDrv = DACBLAST.DRV
joyDrv = NO
mouseDrv = STDMOUSE.DRV
memoryDrv = ARM.DRV
audio=C:\SIERRA\GKCD;D:;D:\sfx;D:\patches;D:\aud
sync=D:\aud
movieDir=C:\SIERRA\GKCD\seq
patchDir=C:\SIERRA\GKCD;D:;D:\patches
====
The main difference with the original is the mouseDrv
and the memoryDrv part.
The movies don't work though, at least, not the intro,
so this could be a problem when they appear
during the game 🙁