Okay, so after a long hiatus, I'm back.
It's really hard to maintain the codebase in C. (Manual memory management is a big pain in the áss)
Here's what I'm going to do:
keep the SPC emulation core in C, turn it into a dynamically loaded library
rewrite the SPCDSP -> IT code in Lua
This way, it will be easier to maintain the code, but I'm not sure how many people here are technical-minded enough to know how to run Lua scripts using the standalone LuaJIT application. I hope I won't leave you behind.