Well apparently the status of the ym2610 (the sound chip used by neogeo/neocd games) isn't saved, I had even forgotten it was not saved because it's extremely rare to have a problem of restoration with it. Actually the fm part is saved, but it's almost never used in these games. The reason why is it's a mess of pointers inside. To sum up : you were just out of luck on this one ! I'll see if things can be improved at least a little...
Ok, just added save ability for quite a few sound chips, including the 2610 required here, but quite a few at the same time. These were things to do for a very long time, but since it's boring and I had to find a way to translate some pointers 1st, it stayed like that for ages. For the pointers I simply manually added a name field so it can now recognize them. I didn't test everything, some games didn't even save the z80 ram, so it was sure to loose all sound in most cases when loading a savegame (all the gunbird driver and quite a few toaplan2 games were like that).
Anyway it should have been done long ago, but better now than never !