Not in 25th anniversary but in Judgement Rites. But you could emulate a MT32 by using an emulator called Munt. It sounds pretty close to the real thing and. if you ask me, is worth the hassle. You have to download and install Munt and find the MT32 roms. Configuring Munt is pretty easy. Afterwards your virtual MT32 will get its own ID. You can then edit the dosbox_st25.conf file and change the midiconfig= line to the new id (probably midiconfig=1 if you don't have a soundcard with differend IDs). Then you should be set and it will sound great!
If you want to try this and perhaps will run into trouble finding the midiID of munt, feel free to ask! :)