I am triggering my JP-8000 from a computer sequencer, and seem to get 8 voices on playback. but when I play the JP's keyboard I only get four voices. What's up?

Are you still playing the keyboard while it's connected to your computer, and sequencer?
Did you remember to turn off the local control? If the local control is on the the keyboard is playing the sound, but is also trying to play it from MIDI.

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