The gate post that plays a tune

 This gate post is on the path from Galmisdale to the caves on Eigg

We have found posts before that emit a note when the wind blows across the bolt hole in the middle. What was new this time was the top hole. Covering it with my hand gave a slightly different note. I should have paid more attention. I was thinking of it as being like a recorder and the fingering changes the length of the same mode stationary wave. But maybe here the trick is that it goes from being a stationary wave in a pipe with both ends open, so a half wavelength, to being a stationary wave in a pipe with one closed end, so a quarter of a wavelength. That would make a bigger difference in pitch.