MIDI setup is working with my iMac through MOTU Digital Performer
MOTU 828 digital audio interface drivers are installed and signal is visible in Garage Band, though not audible even though all the settings are correct. Not sure why.
Next step will be a focused effort on getting digital audio I/O between 828 and Digital Performer.
MOTU has great phone tech support!
They have completely avoided using the phone purgatory systems most companies employ. No dealing with automated menus saying, "For blah-blah-blah press 1, for yada-yada press 2, for bippity-boppity press 8." You just dial a phone number given in the front of the users' manual and an actual, knowledgeable person, who speaks English even, picks up the line to answer your questions.
That's the way customer service should always be.