Hello again!

"Organ pipes can certainly be built in various materials ...
but I cannot understand why the material of the soundboard..."

Of course I mean the windchest of a flute clock or small barrel organ,
made up of 2 or 3 plies of solid wood with holes and grooves in them.
I feel that MDF, properly sealed with shellac, would make an excellent
alternative to alder wood.

Balsa wood has the advantages of excellent availability in perfectly
shaped and perfectly angular blocks, but of course the wood is easily
marked (even a fingernail would have a lasting impact) and the holes
may turn out a bit 'fuzzy' if not drilled with a sharp wood drill.

As I wrote earlier, I've managed to construct a working model of a
simple pneumatic action (membrane chest with bleed hole, inspired by a
similar construction by MMD member Johan Liljencrants), but the question
is simply if balsa wood, even if properly sealed, will be air-tight.

Best regards

Christofer Noering
Stockholm