The Topic Title and Topic Description pose the whole question!

Afsluiter is a dutch term for a shut-off valve. On a large Dutch organ each division usually has an afsluiter meaning that you can engage or disengage an entire division. It has no real practical application in my experience. I would be interested whether Dick Sanderman for example could add any comment here.

The ventil was invented by Cavaillé-Coll for his divided windchests, meaning that the reeds and upperwork can be prepared (ie the stops are drawn) but are only activated by the depression of the relevant pedal (the so-called 'appel'). Its practical application is considerable, look at any French symphonic organ score.

Greetings

Bazuin

Is there any evidence that the device was used make the HW a coupling manual for the other divisions?

I don't think there is any evidence. But it is possible, of course; except that even one manual organs have these things. In German the term "Ventil" refers to exactly what the Dutch call the "Afsluiter" - as well as, confusingly, a few other things as well. Some instruments, for example, have a "Bassventil" - this is the HW / Ped coupler. And pallets are also called "Ventile".


At least one theory is that the ventils were there to shut off any division that might have a cipher. Not really very convincing, as it would be just as efficacious to push in all the stops! Possible that the generally rather leaky chests of old organs might have made it desirable to let the wind which the calcants had been getting up with the sweat of their collective brows into these at the last possible moment.



B

 

Only on a slider soundboard! But then I guess that that's what you're all talking about, rather than Roosevelt or other 'individual pallet'-type chests?

There are some English organs (Conacher especially) where the Pedal action is working the notes permanently and the stop just controls the ventil which either has the wind in the chest or not. In the case of Conacher, specifically, the ventil is usually in the form of a pallet inside the bellows which open to let the wind into the trunk to the chest, operated by a long tracker from the drawstop.

DW