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It sounds as if the organ suffered either a power surge - in which case the damage may be either temporary or permanent, and it might well be permanent by the sound of it, unfortunately - or else its sound generator circuitry and/or audio amplifier has failed.
A prolonged (at least 2 day) powering down and unplugging from the power, might help if the problem is temporary.
If the problem is permanent, then the organ will need servicing by a pro in your region who knows Allen organs of that type. (If you need listings for such a repair-service pro for the Allen MDC line, please let me know your local zip code, or the customer's zip code if it is fairly distant from yours.)
I think the audio processor is more likely, since the organ was playing notes by itself.