There is a lesson on the main PSR Tutorial page.
It is under Lessons / Quick Steps and is called Organ Drawbars.
The lesson is for a PSR-2100, but the info is the same, although the look of your keyboard screens will be different.
It tells you how to save any voices you may want to as well...
Also, on line I found the reference book for the PSR S770 & S970.
It is too large to post here, so I have just posted pages 20 & 21, which have the info for the organ flute info...
Hope it helps!
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