I guess there will need to be a more general solution for the Tandy sound card, like a PM TSR that traps all these things and redirects Tandy sound writes.
As far as i know the Tandy Sound Card approach was to place the sound chip on C0h / 1E0h selectable with a jumper. From what i could understand the last few months i launched the Tandy thread, a TSR is great for interrupt interception but not to read a memory location.
In fact i think having the hardware sit directly on the proper locations is the best approach. It should work great on XT systems (and theoretically it shouldn't be a problem on AT's as well) and no need for software that will require a 386.
For games that DO require to read the TANDY string there's 2 choices: either patch the games like you did or place the TANDY string at the proper location, creating a BIOS extension to do so, like 2M-XBIOS does vias the DOS prompt.
I went as far as changing the Tandy ROM BIOS and changing the string from TANDY to DANDY via hex editing on location F000:C078 and it was not a surprise games that rely on that string started to play PC Speaker music and having monochrome graphics.
It doesn't use the Tandy string, but the Machine ID byte
Can you tell me the exact memory location of the byte?