The sound of an organ is generated by a constant flow of air that is blown through the different pipe sizes. The sound is made either by the air being blown through a narrow gap against a lip, as is the case with the recorder, or by a vibrating reed inside the pipe, as is the case with the clarinet.
Until about a century ago, the compressed air required for the so-called organ wind used to be generated by bellows that were operated with the feet. On large instruments, up to 12 people were needed to perform this strenuous task. Only with the emergence of electricity did organ building make increased use of electric bellows, which, compared to the foot-operated ones, generated a very constant and quiet air flow. But it was always a challenge to design the electric wind generator so that it would not be heard either during quiet pieces of music.
The sophisticated wiring and layout of the controller ensures operation is completely silent and the musical enjoyment is not diminished even during the quietest sounds. The Festo solution also enables a dynamic switch between those parts in the music requiring low air consumption and those needing a full blast of air. The required air pressure of 4.5 millibar remains constant, as one of the two bellows always retains enough reserve air.
The restored instrument with the automated bellows lifting unit has successfully been in action at the college premises in Regensburg since the end of July 2014. The organ has been used in lessons for authentically playing Italian music from the 18th century. Modern technology from Festo has helped to keep a piece of historical music culture alive.