Microsoft seems to have coded something that prevents OPL3 from working at all in NT.

Great card though.

Did you try "Lure of the Tempress" from Revolution?
http://www.revolution.co.uk/_display.php?id=10

This nice little game should run directly under winxp (even without dosbox).

Anyway - wiki says that legacy mode is not supported under windows nt/xp:
http://en.wikipedia.org/wiki/Yamaha_YMF7xx

Moogle! wrote:

Microsoft seems to have coded something that prevents OPL3 from working at all in NT.

Great card though.

Actually, Windows XP did detect the card and installed drivers automatically. In the Device Manager, there was a listing for yamaha legacy audio that included the sound blaster/adlib resources. The midi synthesis that showed up in the control panel was 100% OPL3 and I was able to hear it play. When I actually installed Yamaha's driver, the midi synthesis was changed to samples (XG).

Since the OPL chip works fine in real mode DOS on the same computer, I figured it would work in a Win XP DOSBox using the porttalk driver. I haven't had any luck in making it work with the driver. Has anyone had any luck using porttalk to allow a game to use an adlib or sound blaster?

Not quite the same, but;
I use a YMF-724 card in windows 98, with legacy drivers enabled. I used to configure a windows program 'winamp with adplug plugin' to directly output to port 220 or 388. It worked most of the time.
Currently I use adplug for Dos in a windows dosbox. When I tried that earlier I just heard nothing with certain FM music players: Now I set these programs to first start both a Miles driver 'Opl2.com' + SBPro Mixer, then the actual program is started. With that workaround all is well.
So even if you can access the Opl3 on this card, there is a good chance that it is muted.

Using porttalk I was able to get a true Adlib card working with a DOS game (Doom) in my older PC running Windows XP. The Adlib is an ISA card, of course, and the YMF-724 is a chip running on the PCI bus with an OPL3 chip intergrated in it.

I suppose the PCI bus is the culprit here. The game can access the YMF-724's OPL3 directly in Windows 9x and DOS without any driver loaded. Porttalk works correctly with an ISA Adlib card in Windows XP but does not work with the PCI based YMF-724.