Bingo! I finally found a working link to the very elusive YMF7x4 Utilities 1.0 AKA "Yamaha Utilities"! 😀
The only problem is that it is half in English and half in Japanese. Do we have any members here that can translate the Japanese parts into English and post translated pictures for those of us that can't read Japanese?
The program seems to work, but I'm fumbling around trying to make sense of it.
Unfortunately; however, I've still not yet been successful at FM passthrough in DOSBox.
Perhaps someone else here that can read Japanese will be able to use the Yamaha Utilities and figure out a way.
Edit: I just found out through translating the readme using Google Translate that it says that many of the settings require a reboot to take effect. I was not taking this into account before and so that may play a major role in getting the desired results. Anyone that plays around with this software should definitely take this new info into account.
Edit: I just discovered through the Yamaha Utilities that the driver YDSXGDK.SYS didn't automatically install using the previously posted install method so I manually moved it to the System32 and System32\drivers directory. So far I've not noticed any difference this has made, but it must play a role in something or else Yamaha Utilities wouldn't have had it grayed out before and now it's not grayed out. Anybody know what YDSXGDK.SYS does and if it's important?
Edit: I finally did it!!! I successfully got OPL3 FM passthrough to DOSBox inside Windows 7 32bit! I will be writing a full guide in a new post soon.
Edit: The guide is finished and posted. I hope it will be of help to others struggling to get this working. DOSBox Guide To OPL3 Passthrough Using Yamaha YMF7x4 Series Sound Cards (Unsupported)
"There are only 10 types of people in the world; those who understand binary, and those who don't."