The medieval music organ at saint Michel abbey in northern France

arrages
These are the partitions which delimit the grooves. These partitions are assembled within the frame.

ellows
Until the advent of electricity, the only system for supplying the organ with wind consisted of a set of bellows (2 to 8) operated by one or several persons. The bellows served both as reservoir and pressure regulator (the lid of the bellows was weighted for this purpose).
During the nineteenth century, accordion-folded reservoirs supplied by pumps, which provided a steadier supply of wind, began to be more widely used. The appearance of the electric motor made it possible to replace the pump operators by blowers that sent the air into a pressure regulating reservoir.
      Only 50 to 120 mm of hydraulic pressure is required for an organ.

hoir Organ
The term choir organ indicates a sound unit controlled by its own keyboard. it is most often in its own cabinet facing the main keyboard, inserted in the balustrade of the organ loft. But it can sometimes be contained in the organ chest, placed between the keyboards and the great organ.

rgan builder
Craftsman, or Company manager, he is responsible for the building of the organ. The trade demands a very high qualification in a multitude of technical fields: joinery, cabinet making, smelting and working different alloys, mechanisation, electricity, piping - and also a sound knowledge of musicology, ancient instrument, industrial design, without forgetting the qualities of company director having to deal with market overt, all the financial constraints, and the training of apprentices and craftsmen.
In France there are about fifty workshops of which some regroup several craftsmen. A Professional Training Centre has been created at Eschau which has a lot of activity.

rgan chest
Here we find the different acoustic divisions which are brought into play by the organist. Taking into account the size of the organ (the number of stops) and the hall where it is placed, the chest is generally monumental. Like the case of a cello, it contributes to the quality of the sound emitted.

anks (Classification of)
The ranks have open or closed pipes; these are in wood or metal (an alloy of tin and lead, variable according to the tone required, and this concerns especially the upper sound range).
Groups of Ranks.
1. The Principals which may be the Front Pipes, the bourdons 16 - 8, the flutes 8 - 4, the diapason 4, the doublet 2 for Saint-Michel;
2.The Reeds;
3.The group of mutations or mixtures: a sound is obtained by the addition of the singing of several pipes on one note. Their role is to enrich the fundamental notes by their harmonics.