Success! I've fixed it! 😀 😁
It was a good call for me to install the DOS drivers for my sound card! It set everything up correctly by default. And it helped me isolate the root cause.
Initially, I tried playing the game on my test rig, but still had the same issue. Getting the Pentium II was definitely a smart choice. I used my first Pentium III 450Mhz, which caused the game to lock up before speech could play. Switching to the Pentium II fixes that, so that's definitely a CPU issue.
But the crashing outside the SCUMM Bar - the games look to use WSS as well as the Sound Blaster and General MIDI. When the door to the SCUMM Bar is opened, it should play a sound effect before entering. Prior to the crash, nothing plays. I was only getting music and speech. It looks as though sound effects are done with the Windows Sound System audio. Unisound doesn't give any manual options, I don't think. Volumes are controlled with command switches, but I'm not sure if channels/resources can be set...? SETYMF does, thankfully. And the main channel for WSS was set wrong. It was set to A20 for some reason. It needed to be 530h. And its own IRQ and DMA need to be set right. The default DOS drivers did that, too. They were set to 5 and 0 respectively. SETYMF doesn't list IRQ and DMA directly under WSS so that leaves IRQ B and DMA B. So I set WSS from A to B and then IRQ B was set to 7 (as 5 was taken) and DMA B was set to 0. Everything appears to be working correctly. 😁
There's still a chance it could crash, which will probably be resolved by disabling the L2 cache. Will have to play through the game some for testing. As well as testing Monkey Island 2 Talkie.
Time to write some notes for future reference. 😀
Also, I noticed my Pentium II gets quite hot. Will need to take the fan off one of my Pentium IIIs.
OS: Windows 98 SE
CPU: Slot 1 Pentium III Coppermine 933MHz (SL448)
RAM: Kingston 256MB 133MHz
GPU: Nvidia 16MB Riva TNT/128MB Geforce 4 Ti 4200
Motherboard: ABit AB-BE6-II Intel 440BX
Sound Card: Sound Blaster Live Value CT4670