The Carnivore2 is detected as the Musical Memory Mapper. This is because the Carnivore2 has implemented the extra mapping functions of the MMM, but does not support the DCSG sound chip.
This prevents Carnivore2 users from using DCSG sound expansions. Either a way to distinguish them needs to be found, or it would have to explicitly detect the Carnivore2 and then exclude its primary slot from the MMM search, but I’d rather not do that.
Luckily the Carnivore2 is emulated in openMSX. But I wonder why it supports those MMM functions, they’re not very useful if the cartridge itself already has ROM mapper emulation.
Fixed bfcbaa36071d.
After the above fix, it would still not always work:
Press ESC on the C2 boot screen and VGMPlay sees the Carnivore2 and doesn’t detect it as MMM, but when you press ENTER it doesn’t work.
This has been fixed in the Carnivore2 firmware earlier this year, see this thread.