Compressed air

What it means

The organ is a wind instrument in the literal sense: its pipes sound because air is supplied to them under even overpressure. Today this wind is produced by electric blowers, formerly by bellows that were trodden by bellows-pumpers (Kalkanten). From there the air flows into reservoir bellows, which even out the pressure, and on into the wind chests on which the pipes stand. Only when a key opens a valve does wind reach the pipe concerned. The wind pressure is measured in millimetres of water column and is, for each instrument, part of its tonal design.

Musical use

The wind pressure determines volume, response, and tone colour of the pipes and is matched at the time of building to the volume of the room and to the tonal ideal; it is not a value that the player changes. For music-making an important property follows from this: as long as the key is held down, the note continues to sound unchanged — the organ knows no decay and no touch dynamics. Expression therefore arises through registration, articulation, handling of time, and, where applicable, the swell box. Instruments with an older bellows system show a slight wavering of the wind, which, depending on the view, is felt as lively or is compensated by modern technology.

Performance practice

Take care that the blower is switched on before playing and the bellows has had time to fill. With very large registrations, expect an audible yielding of the wind, especially on older instruments; distribute dense chords then rather into the middle register. Avoid holding several reed stops in the low register at once if the instrument responds weakly to wind. Disturbing noises such as howling or ciphering of individual pipes are the task of the organ builder, not of the player. Pass on such observations, stating stop and note.

Bear in mind that the wind does not arrive equally fast everywhere in the instrument: after longer pauses or with heavy use of stops, the response can be delayed, especially in low registers. Start a little earlier there. Some historical instruments show a slight wavering of the wind that belongs to the sound picture and is not to be treated as a defect. Take care to switch the blower on in good time and off again after playing, and report unusual noises to the organ builder, stating stop and note.