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Pure tuning
Eivind Groven's project
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Groven's idea and technology

Groven was only thirteen years old when he encountered the problem of pure tuning while tuning a "toy harp". He could not get it tuned perfectly in all keys, and wondered whether there was something wrong with his hearing.

The problem is linked to tempered tuning, which in short can be described as a series of compromises in which pure intervals are sacrificed in order to allow instruments to be played in all keys without having to be retuned. The tempered scale replaces the natural scale, and the pitch differences are large enough for Groven to describe them as unclear. He thinks that these impure intervals create "disquiet, reducing the beauty of the music and the enjoyment of the listener" (Groven 1948, p. 15).

This observation spurred Groven to work on developing a practical and theoretical system for pure tuning. The publications Naturskalaen (The Natural Scale) (1927), Temperering og renstemming (Temperament and Pure Tuning) (1948), and Renstemningsautomaten (The Pure Tuning Automat) (1968) provide the theoretical foundation for his system with 36 pitches/octave, that he found sufficient: "...any modulation can be solved within a tone field of 36 different pitches in the octave, developed through pure tuning. If one wants to add more pitches to the system, the result can become better in some situations. But the advantage of this is hardly worth the effort (Groven 1948, p. 80).

As a practical parallel to the theoretical development, Eivind Groven had several instruments built for him. In 1936, a harmonium was built at Gjøvik Organ and Harmonium Factory, and each key had three pitches. The instrument used a semi-automatic switching technique, and was a bit cumbersome. During 1939, Groven started work on a tone selection automat that could be controlled by impulses directly from the keyboard. The little difference in time between when the finger hit the key and when the tone actually started could now be used, and operation of the system was automatic while the performer was playing, producing pure intervals. During the next five years, Groven developed the first unique pure tuning automat. It was built from discarded relays from the national telephone company, and laboriously developed with small means. In 1953, the first pipe organ was completed, monophonic and with 36 pitches/octave. The instrument was built by J. H. Jørgensen's organ factory, and was first installed in Trefoldighetskirken in Oslo. Since that time, it has been installed in Fagerborg Church, and is now located in Groven's organ house at Ekeberg, Oslo. Groven also built a new automat, with relays from Elektrisk Byrå.

Groven continued his practical work with the development of an electronic organ. This was done in collaboration with Ragnar Bogstad, and the instrument was completed in 1965. The organ had 33 timbres, some of them rare - such as goat horns, willow flute and bagpipe, and 43 pitches. Here, transistors replaced relays, and Bjørn Raad at the Central Institute for Industrial Research built this transistor automat containing approximately 1,400 transistors, according to Groven's diagrams and designs. The electronic organ was originally located in Eivind Groven's study at Ekeberg in "The lower house", where it was also made, but for a shorter time it was moved to Vålerenga Church in conjunction with a large concert organized around the capabilities of this organ. After the concert, it was returned to Ekeberg, and after the organ house was built, it was moved there - still keeping its 43-division of the octave. During the 1970s, Groven customized a standard factory-made electric Sonata-organ for pure tuning, and returned to the solution with 36 pitches/octave. Both the pipe orgen and the Sonata-organ were connected to the electronic automat that needed to be adjusted to the solution with 36 notes/octave in order to work with the pipe orgen. At that point, the first electronic organ was disconnected and the relay automat becam obsolete. This means that before teh Sonata-organ cam, the pipe organ was still connected to the relay automat, and the old electronic organ was working. The electronic automat was originally made for this.

The harmonium is included in the collections of the Norwegian Folk Museum, and the pipe organ and both electrical organs are placed in the Organ House. However, the electric organ with the 43-pitch-division is not operative.

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In collaboration with Eivind Grovens Institutt for renstemming