Ref. Niels Berkers in 210528 MMD. To my understanding, the Debierre pipe
works as following: each note is fed by its own toe, as clearly seen in
Philippe Crasse's post in MMDigest 210526. These toes all have one-way
valves to prevent backflow into the other key valves.

Of course, for the fundamental tone of the pipe, it simply functions as
a regular organ pipe; for the added notes, a small amount of the air is
directed away from the labia and into the pneumatic pouches which then
lift open the desired key. These pouches are very easy to see on
Philippe's post.

Unlike later Compton and Wurlitzer multi-tone pipes, these Debierre
style pipes do not require any relay of any kind to work, and they will
function on any kind of windchest. If any multi-tone pipes are to be put
into a fair or dance organ, I'd put my money on it being one of the
Debierre-type pipes.

Christian Tedesco