Thanks to all. I'll post extracts on my "someone is wrong" file.
I didn't immediately post it as bad physics, because I thought there was a chance that the coupling would work (slightly) because of low Q on the part of the organ pipe vibration. I also (as one posted) thought the coupling would be "difficult" unless the inside of the tube were rough. This demo. reminds me of an unsuccessful discussion on another list of "why" longitudinal and transverse waves in solids had different speeds (e.g. earthquakes). I pointed out shear and Young's moduli had different values, inter alia, but this was too much for the HS teachers. Here's a, I think, very good, demo of such.