Warning ... extreme novice is writing the following ...

Continuing from the Subject of the post:

However, a downloaded midi file import has a brief 2 bars where a "harp" (bank 0, patch 46) (Channel 10) run up instead plays a variety of the PSR-E333 drum type sounds.  Far as I can tell, however, the other tracks set to different channels use only the #001 Voice (grand piano)

The "enable MIDI output" section of sf2 play has a "PROGRAM" setting which I don't know anything about yet.  Could that have a bearing on my confusion?