It usually depends on what your controller keyboard can output,
E.g. My Abacus has 3 outputs per each physical Midi Output, (Manuals, Accompaniment (Styles) and Sequencer.) therefore I could set the 16 track Sequencer to the first 16 channels of the SD 2 and the Acc and/or Manuals to the remaining 16.
Hope this helps

Bill
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English Riviera:
Live entertainment, Real Ale, Great Scenery, Great Beaches, why would anyone want to live anywhere else (I�m definitely staying put).