I shared this in the PicoGUS thread too, but I think it might be relevant to some people here as well:
A somewhat related project was just launched, called Picovox.
As the name implies, the Picovox is kind of like a PicoGUS or a PicoMEM, only it connects to a parallel port instead of an ISA slot, and it aims to emulate most parallel port sound devices. There is already partial support for the Covox Speech Thing, FTL sound adapter, Stereo-on-1, Disney Sound Source (DSS) and OPL2LPT.
As with the PicoMEM, non-sound functionality is also being considered as a future addition. For instance a virtual printer that saves "prints" as PDF files to an SD card. So that would in essence make it a more of a multi-purpose software-defined parallel port device. But at least initially, sound device emulation will be the primary goal.
The developer, @jansakos, is working on this for his Bachelor's thesis, and aims to add support for additional devices as well. Help is welcome!