07/07/2021
More on diaphones:
Diaphones are a "valvular" reed. So instead of a brass reed closing on a brass shallot (other metals might be used), there is a round disk (valve) on a steel spring, with a weight affixed to it. The tone is generated by this valve closing and opening rapidly.
The valve seats against a leather face, while the other end of the spring is held tight in a pair of leather faced clamps. Adjusting where the clamps hold the spring, tunes the note.
Diaphones are unique in that the pitch does not change with an increase in pressure, and they can be made to play on extremely high pressures (even measured in PSI).
Common cousins of diaphones are fog horns at lighthouses, and air horns on trucks, trains, and ships.
Diaphones are most often found in theater organs with resonators made of either metal or wood. They can also be found sometimes in church and concert organs built during the theater organ period. They have a very quick response at 16' pitch, with lots of fundamental tone.
