When the organist presses a key or pedal, they mechanically open a valve, allowing air to flow into the respective organ pipe. When it hits the labium (the flue pipe which produces sound through the vibration of air molecules), it eventually creates the characteristic sound of an organ. This air is called 'wind' in organ terminology and comes from one or more large bellows that were filled by so-called organ pedals or 'calcants'. They did this by stepping on a lever mounted on each of the bellows; after stepping on it (and filling the bellows), the bellows collapsed by their own weight, thereby forcing the wind towards the organ. Operating these levers was a tiring job that required a whole team to produce sufficient wind in large organs with many bellows. Even then, many organists were troubled by the fact that even with so many people it is not always easy to create the required constant wind pressure.
Electric drive
These problems were solved when technology allowed organ ‘wind’ to be generated using a ‘wind’ machine or electric blower: a combination of electrically driven pumps and fans that produce constant and relatively quiet ‘wind’. A blessing: no more people needed and always a constant ‘wind’ pressure. Marijn Slappendel is employed by Elbertse & Van Vulpen Orgelmakers and knows: 'A blessing in terms of labour and consistancy of air pressure but the new solution also brought new problems. For example, the electric wind generator produces noise that can disturb soft organ music. In addition, this way of generating wind causes 'restlessness in the sound of the organ'. This is a difficult aspect to define not easy to measure, but for organists and connoisseurs an unmissable limitation of an electric wind generator.
Village church Woubrugge
As an organ builder, Elbertse & Van Vulpen specialises in both building new organs and (increasingly) restoring old organs. There was a long-standing desire to eliminate the aforementioned 'restlessness' by lifting the bellows in the 'old' way instead of filling them with wind using fans. 'Obviously it was not the intention to breathe new life into the calcants either,' Marijn points out, 'But somewhere it had to be possible to find a technical solution that fills the bellows with air as if by a calcant.'
Marijn was given an idea when he read an article describing how Festo had used a servo motor in combination with a controller to automatically open the bellows of a small Italian organ at the conservatory in Regensburg. "The solution in this form was not suitable for larger organs, but it did indicate that there were possibilities," Marijn believes.
With this in mind, he contacted Festo when the organ maker was commissioned to restore the Mitterreither organ from the Dorpskerk in Woubrugge. This late 18th-century organ (1794) with over a thousand organ pipes was in dire need of restoration including an organ case full of cracks and crevices, damaged and soiled pipes and leaking wind chests. 'We wanted to give this organ back its authentic sound and came up with a construction in which a shaft with a carrier would push up the bellows from below so that it could fill with air. By lowering the shaft back down faster than the bellows themselves, the latter can sink back down completely on its own weight and thus produce wind for the organ in an authentic way.'