Did you read this on download page? Other experimental builds also will not be supported.

Do not report any bug to developers because these builds are experimental and NOT officially supported.
I recommend you to use clean SVN build first before using my build.

Does your GUS setup work in other games?

You can send me the game and I can test it on a real GUS if you want.

Tested with my RtZ cd version (1.1).
This game work perfectly with GUS if you delete SBOS -f string from rtz.bat
Unfortunately, SBOS emulation do not work with DosBox for me.

Thanks for the responses. I have the same issue with the official .74 release so providing support shouldn't be a concern. My GUS setup does work with other games, and my CD version is also 1.1.

Below is the content of my rtz.bat file, which doesn't have a SBOS line to purge. The game is configured to use SB for digital audio, and Ultrasound for music.

@echo off
C:
cd \RTOZORK
LOADHIGH DRIVERS\SBPRO
MADECD RTZCD -M:DRIVERS\GF1MIDI -O -X -P:D:\
DRIVERS\SBPRO u

If I configure GUS for both digital audio and music, I have a different issue in which the game drops back to the DOS prompt with a...
Insufficient Free DOS Memory
5440 Bytes Additional Free Memory Required
...as I believe DOSBox provides as much memory as is possible with a DOS install (i.e. 632Kb in my current install), not sure there is any way to resolve that. Even if one could I'm guessing it would still hang before the game starts.

Return to Zork is pretty flakey at the best of times. Even back in the day on a 486 I had to load the game and exit then start it again or the CD music wouldn't work.

I have an original copy of the game but I don't have a GUS to test with unfortunately.

Which version are you running? There is a 1.2 patch available which has some updated sound drivers. http://www.patches-scrolls.de/return_to_zork.php

I believe SCUMMVM will play Return to Zork as well, have you tried that?

Yes, I have it working in ScummVM, but my main interest at the moment was in hearing the GUS music which ScummVM doesn't provide.

I have the same issue with the 1.2 patch installed. Though I noticed the following in the DOSBox status window...
Illegal read from 445a4002, CS:IP 0: 198
...or...
Illegal read from 44596021, CS:IP 0: 198

Alternately, the game will crash back to the prompt still in 13h mode, with the message...
Sound Driver unloaded