Yes, I confirm this ;-)
The strange thing is that I was able to trace the Z80 activity and I confirm also that it's accessing (write and read) the mapped FM memory ... what do you think I should do to trace that further and see where the problem comes from ?

Note that in Genesis Plus, Sound Buffers are updated after each write and then completed at the end of the frame... I wonder also if that is really correct or could lead to such sound issue

thanks for your response

> A lot of games use the Z80 for FM and PSG access and let the 68K handle the DAC
> port (which is part of the YM2612, technically.) Some games may also drive the
> PSG with the 68K, IIRC.
>
> If you can confirm that you're not hearing anything but DAC, then it's
> definitely an issue with the Z80 not running or communicating properly.
>
>