The blower and bellows tab

It is generally agreed by experts, that it is the wind behavior which makes the beauty of the organ sound. In early times, wedge bellows were used in organs which were pulled up by "calcants". There were usually several sets of bellows to feed the organ so that the wind achieved some stability.  Nevertheless, the procedure of pumping and also the changing torque of the falling moving board as the bellows were deflating, caused slight changes in pressure, slight oscilations which affected the pipe speech. Also, the wind stability was so delicate that playing on one manual with just one or two stops affected the speech of pipes played on a different manual. After the parallel rise bellows were invented, and after organ blowers invaded churches, these subtle wind behavior was lost to great deal. With the help of Hauptwerk, we can now model the original situation of the hand pumped bellows and indeed, it is completely new experience of the organ sound.

The reconstruction of the wind compartments to the original Schnitger specification - in BETA stage now.

Originally, the instrument had 12 wedge bellows in parallel connection.  All bellows feed two common trunks (left and right) where all the divisions (which mostly are also divided to the left and right side - called C and C# side) are fed from. The bellows are of the wedge type and are operated by hidden calcants. However, instead of hand pumping, we use a hidden blower to feed the bellows, since the way to feed bellows by lifting the top moving board "mechanically" does not seem to be supported by Hauptwerk at present. Therefore, a set of additional valves had to be constructed for the wind model to be stable. There are two valves: inlet and exhaust. Inlet valve opens when the bellows is empty (extension = 0 mm) and at the same moment the exhaust valve closes. The bellows is thus detached from the rest of the wind compartments which is essential for the stability of the wind model. In this way the bellows is fed from the blower. When the extension reaches the maximum (i.e. when the bellows is full), the inlet valve closes and the process of filling the bellows has ended. At this point, the pressure inside bellows takes some oscilations before it reaches the stable state. Therefore, it would not be very good to attach the full bellows to the system, as these oscilations would disturb its stability. To lessen the shock of attaching the full bellows to the rest of the wind compartments again, we wait until the moving board falls down a bit (because of the bellows leakage) because at that moment the condition of the bellows is pretty stable. Only then the exhaust valve opens again.

The indication of the bellows extension is shown. The small icons above this indication are showing the state of the inlet and exhaust valves of the given bellows. The left is inlet, the right is the exhaust valve. These operate automatically, but they are also clickable, if you want to achieve some special behavior. In addition, there is also the master inlet valve above each set of bellows which is clickable and can be used to disable the bellows temporarily if desired. In this way, the user may choose freely how many bellows will operate at any given moment!

In the left bottom corner, there is the blower switch (you can turn the "calcants" off or on for the entire organ) - if you switch it off, the bellows will deflate after a while and the organ will be without wind - i.e. without any sound. Also, you can alternatively choose to bypass the non-return valve present at the foot of each the set of bellows. This can produce different behavior of the wind system if desired. In the right bottom corner, there is the main trunk inlet valve shown in a form of continuous controller. Clicking on the valve, you can make the aperture of the wind trunk wider of narrower, allowing more or less air to the whole system if desired.

There is further set of valves which enable the user to select from two scenarios: either all 12 bellows operate to feed the entire instrument, or first 4 sets of bellows operate the Pedal division only, while the rest (8 bellows) feed the other divisions. The choice is done by clicking on the label "Independent Pedal bellows" in the left lower corner.

Each division can be set to have the windchest divided into two sides (left-right, C-C#) or to have one single windchest. The figure shows the screen layout.