If I understood correctly, from v0.8.2 openMSX now supports MIDI output on Mac OS-X.
I tried the following command on the shell, but the MIDI still doesn't produce any sound:
plug msx-midi-out Virtual
Are any other commands/configuration required?
PS: It may be a good idea to update the manual with Windows and Mac examples:
OpenMSX-0.8.2-dev12690 on Mac OS-X 10.6.8 emulating an MSX FS-A1GT
Games tested: MoonLight Saga Promo, Illusion City