A German-made organ for the Leon cathedral

The Santa Maria Cathedral in Leon was built in the 13th and 14th centuries and for the past 35 years it has hosted an annual international organ festival, drawing some of the world's greatest organists and ensembles, as well as international audiences. After deciding the old organ was no longer up to the task, a music foundation began to push for a new instrument. Getting it would take decades.

The Cathedral is an international tourist destination and is particularly famous for its original medieval stained-glass windows of intense color. Organ maker Philipp Klais first came to the cathedral with his father in the late 80s. For 20 years they kept up contact with church officials, even submitting three designs before finally getting the go ahead to build the new organ in 2010.

It was a dream come true for Klais, whose great-grandfather, grandfather and father were all organ makers. He now heads the family workshop. "Such a project, one that takes decades, where there is no money at first, where no one knows if it will become reality — it can only be realized with an extremely generous amount of idealism from all involved parties," he said of the Leon organ project.

The project's biggest challenges were the interpersonal ones that arise when working on something involving many stakeholders. But according to Klais, there weren't any major problems. "Naturally, there was always the worry that deep, dark, loud, strong frequencies could damage the windows." But he said this has never happened in cathedrals elsewhere – and it hasn't happened in Leon.

Following an official celebration for the commission of the new organ, the physical work got started in the Klais workshop in Bonn, where some 60 people are employed. According to Philipp Klais, it took one year to create the technical drawings and the construction plans and another year to build the organ components in the workshop.

The Leon organ has a total of 4,130 tubes — each is an individual tone! Ninety-three are made of wood, with the rest made of tin. The Klais workshop keeps plenty of bars of the metal on hand in a room they jokingly called "the bank." The bars are taken, melted down, and rolled out into long flat sections that the tubes will eventually be made from.

Revolutionary French organist Jean Guillou was intricately involved in the new organ's design. Klais explained that according to Guillou, an organ should function like a choir: "Each individual pipe has a soloist's job but must also sound beautifully together with hundreds and thousands of other pipes." The pipes' four groupings let the sound surround the listener for a more direct experience.

The Leon organ is electric, meaning a current is used to control which pipes sound at a particular time. Some of the pipes are located in cupboards within the stone walls of the cathedral, accessible via narrow spiral staircases. It's a tight squeeze but at least once a year a Klais team member will go in there to make sure the pipes are well-tuned — and that no little birds have flown in!

The Leon pipes cover a gargantuan range in frequencies. The deepest pipe can sound a note of 32 hertz, a crackling tone at the bottom edge of human hearing. In contrast, the highest pipe can sound at 16,000-17,000 hertz, which is at the very upper threshold. Children can hear such high tones more clearly than adults — and some can't hear them at all.

Once built in Bonn, the new organ's parts were loaded onto a truck and driven to Leon. It then took Klais workers roughly four more months of on-site work to install and fine tune the instrument. The organ was unveiled in September 2013, with Jean Guillou himself performing. Today you can hear it ring out at mass, for weddings and, of course, at the 36th International Organ Festival in Fall 2019.