I tried your suggestion, Aaron, and it does work for clamping the output to following stages. cleaning up the glitchy sounds. So that is a potential workaround for now. Thanks for the tip.

In the long term, something more thorough is necessary, both because the out-of-range voltages will still feed back to the op-amp inputs and thus affect the op-amp circuit's own behavior, and because it is wasteful to include components like the voltage-limiting diodes within the op-amp model if they don't actually perform the function they're supposed to.

Well it writes to the MIDI register which we don't handle at all currently. It might wait for an interrupt from it.

MAME's Linux documentation - aka the MAN files:
https://github.com/mamedev/mame/tree/master/docs/man

Could one of our friendly Linux devs or package maintainers please check that the MAN files are still in sync with https://github.com/mamedev/mame/tree/master/docs/source / https://docs.mamedev.org/
at some point? And if not, re-sync them?

It doesn't need to be right away, but it would be nice to know if they were in sync. We do have people who tend to look after such things but most of them are Windows users.