I just received this information from Nicholas Rezmerski -- thanks for the info, Nicholas!
For those of you who'd like to remix old video game music or use OPL2 instruments to write your own music, YouTube user "theycallmebruceful" (I think he's bsutherland on github.io) "wrapped the OPL2 emulation code from DOSBox (hardware/dbopl.c) in a VST instrument. Almost all the available parameters are programmable. Each instance of the plugin emulates a complete chip."
He goes on to say that he loaded MIDI note data ripped from the game [Syndicate] into Renoise, and loaded an instance of the VST for each instrument. Instrument parameters were programmed as closely as possible to the originals by running the game in DOSBox and capturing the register writes to the OPL device. He's named the VST JuceOPLVSTi.
Here's the YouTube demo: http://www.youtube.com/watch?v=HI7U5XxTSW0
And here's the VST (32 bit): http://bsutherland.github.io/JuceOPLVSTi/
When I have some spare time, I'm going to check this out. I'll be interested in what any of you have to say about it after you try it out.
Nicholas said he has been listening to Doom midi files using this plugin.