Howard Wyman is correct, there should be a regulator between the main
wind supply and the accordion in a dance organ.  I have fully restored
my own Arburo so am familiar with this area.

The regulator is of the conventional hinged bellows type.  This
employs a large hinged bellows with an internal knife valve cutting
the inlet flow when the bellows opens under pressure from the main
supply.  The valve should be open when the bellows is closed and closes
as the bellows opens to its working position.

The bellows is held closed by springs designed such that at the point
when the knife valve closes, the pressure inside the bellows is the
correct pressure for the accordion.  Any demand from the regulator
bellows causes it to close slightly, thus allowing more supply wind to
enter up to the point when the supply is again closed by the knife
valve.  The pressure in the bellows always stays at the desired value.

Due to the large demands made by the accordion, the regulator bellows
is large.  In my organ it is around 8 inches by 12 inches.

Nicholas Simons, GB