Fresh wind through old pipes

Automated air supply in historical organs

Whether majestic or modest, delicate or complex, whether in a classical church setting or in modern rock music, the organ is the queen of musical instruments. The variety of its sounds remains unequalled. Whilst on modern organs the sound is generated electronically, air still sets the tone on classic instruments. Instead of relying on human muscle power, however, the arduous work of generating wind is now carried out by machines.

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.

Bellows generate organ wind

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.

Electric motors for driving bellows

When it comes to restoring old instruments, however, organ builders try wherever possible to keep the historical bellows in order to preserve the original sound of the organ. Electric motors are often used to move the bellows up and down, so the wind for an organ is generated automatically instead of by a human hand. This was precisely how the historical organ at the College of Catholic Church Music and Musical Education in Regensburg, which was built in 1752 by Antonio Pilotti from Bologna in typical Italian style, was restored – by installing an automatic bellows unit.

The brief for the Jörg Bente organ workshop was that the original historical function had to be preserved and that the organ, apart from the main switch, should not be fitted with either a programmable logic controller (PLC) or other control components. Together with experts from Festo, the decision was ultimately made to use the electric motor series EMMS-AS-70 as well as a controller from the series CMMP to control the motors.

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.

Automation at the music college

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.