Hi:
If you are using Tune 1000 or (Hit Tracks) or any professional/commercial midi files, usually track # 5 is the Harmony, all you have to do is to go to the menu of the Harmonizer and select the track # 5, for more precise or step by step, check you owners manual or go to the PSR Tutorials.
If you are not using this midi file type, then, you must write in track # 5 the harmony notes you wish to have, in most software sequencers is possible to do it.
Hope it helps.
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mdorantes
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mdorantes