AWJ (Alex Jackson) added support for the extended V25/V35 features to the NEC V20/V30 core in MAME.
These features (timers, memory-mapped register banking, custom interrupt controller) are used by the sound programs of several Toaplan titles. He then hooked things up properly in the driver, giving full sound to Batsugun.
Batsugun has unencrypted sound code, so was the easiest one to get running.
V-Five / Grindstormer, Fix Eight, Knuckle Bash, and Dogyuun will also benefit from this once their sound code has been fully decrypted. This is just a matter of time and a bit of effort in figuring out the programs.
For the remaining Toaplan games (Teki Paki, Vimana, Fire Shark, Ghox, Whoopee JPN version) the sound MCUs need decapping, which will require funding / donations for this purpose.
And for those interested:
* 12th March 2000: Quench sent in a Toaplan2 update with support for Ghox, V-Five, Dogyuun and Batsugun.
* 0.139u3: David Haywood fixed incorrect VDP mixing in Batsugun.
and now 0.141u1 (when it arrives) will finally have the game in full working order!
Combining my previous graphic fixes in 0.139u3 with the complete sound emulation from AWJ, means that for the first time ever the game will be 100% working in an emulator! It’s only taken almost 11 years :-)