You can see that the channels are labeled YM2608, which is one of the many four-operator FM chips from Yamaha used in consoles and PCs (like the Genesis and AdLib).

https://en.wikipedia.org/wiki/Yamaha_YM2608

Like the IBM-compatible PCs, the PC-98 series was available with various different sound options.

It's a programmable synthesizer. You can of course implement the MT-32 instrument line-up with it.