@OG - I have been regularly pulling git and building with SOURCES=src/mame/drivers/mindset.cpp TOOLS=1 REGENIE=1, and the sound output is still very wrong, vyper's output is much too fast, and is very distorted (and mode 2 sounds do not have their sine mask applied, so the frequencies heard are wrong),

for reference, here is vyper being played from actual hardware.

https://www.youtube.com/watch?v=DUROL6xs3k4

-Thom