These rips are awesome! I might mention, that personally, I'm looking for rips of GB Genjin 2 aka Bonk's Revenge & GB Genjin Chikun (something or other, I forget the full name). Is there any kind of tool that someone like me can use to make them myself, or is it pretty difficult?
Music drivers and formats vary widely from game to game, so there isn't a tool that does everything for you. What you need to know is the assembly language for the system's CPU, how to interface with the sound registers, how memory is organized, bankswitching, interrupt handling, and of course the rip format you will be going to use.
As for helpful tools, nothing beats an emulator with an integrated debugger. I use FCEUXDSP for NSF rips and BGB for GBS rips. I don't know of any PC-Engine emulator with debugging features, so in this case, a disassembler is your best friend (though a debugger would make things so much easier). Also, you'll want a hex editor to put everything together.
In conclusion, the barrier of entry is very high if you aren't used to low-level programming. As for the two games you mentioned, I'll look into them when I need to take a break from Kabuki Den.
EDIT: Okay, got around to those GB Genjin rips much sooner than I thought. I have updated my page with the rips.
I could happily help you with Snatcher (my playlist has been waiting for a rip for four years!). If I understood correctly, you need a save state (memory dump) for every tune while it's playing?
Actually, now that I think about, one should probably be enough. If all the PSG music is accessible from a sound test, assuming no loading time when accessing different tracks, then all of the music should be in the save state.