> My 20-note Hofbauer always plays one note even when the tracker bar
> is taped over.

Did you regulate the valve correctly?  If the valve screw is
completely shut (screwed in), then the note may play even with
a taped-over tracker bar hole (as no air can go below the membrane
and lift it to close the tube to the pipe).

After getting an organ from a different climate, and typically
also once in spring, and once around winter, you will have to (or
you should( regulate the valves anyway to get correct repetition and
no ciphers.

Harald Mueller
Bavaria