The second entry this week is the third and final instalment on the instruments made by the Compton Organ company. The first post gave an overview of the different organs produced by the company, whilst the second took a closer look at the underlying principles behind the Electrostatic tone generation developed and used by Compton. This final post will detail the inner workings of a surviving, fully working Compton 357 C.S Electrone organ.
For illustrative purposes I arranged to take photographs of a real 357 in a local place of worship. This organ was a new installation in the mid 1960’s when the building was completed. It has seen regular use since its installation and continues to be used at least once a week for services and events. I had the fortune of meeting the current service engineer and learning about some of the instrument’s history.
This engineer had also by chance spent time working in the Compton factory assembling organs. He told me that no two examples of the same Compton model actually left the factory the alike. The designs would be broadly the uniform but individual assembly engineers had their own habits and idiosyncrasies that would manifest themselves as variations in the instrument construction.
It has undergone servicing and maintenance since at least the mid 1980’s, the most significant of which involved removing the original valve amplifier and replacing it with a solid-state alternative. This was a common modification carried out on valve amplifier Electrones, organ owners found they were having to spend large amounts of money to replace tubes and solid-state amps were therefore much cheaper and more reliable.
This is a photograph of the rear of the Compton 357 with the back panel removed. Broadly speaking the organ can be divided into four sections; the top third consists of the voicing resistors section, the middle houses the tone generators and the bottom comprises the amplifiers and pedals. The fourth section concerns the key action, unfortunately this could not be photographed without further dismantling the instrument.
When a stop is activated on the from panel, the generator electrodes attributed to the combination of partials required to reproduce that particular timbre will be energised. The voicing resistors purpose is to act as a matrix to route the signals from the keyboard to energise the correct generator electrodes as determined by the state of the stop switches.
This section comprises the twelve Electrostatic generators referenced in the second Compton post. All twelve generators are rotated using a pulley and belt system powered by a single motor. There is an additional layer of fibreboard material encasing the generators in an effort to limit the amount of mechanical noise produced by the motor and pulleys.
Note that the pulleys decrease in diameter relative to the chromatic note attributed to each generator. The generator on the far left is the highest note of the chromatic series (B) and has the smallest pulley, whilst the generator on the far right is the lowest note (C) and consequently has the largest pulley. This means that the rotor disc on the lowest note (C) is rotating at a much slower rate than the highest note (B). This gearing would have been specifically engineered in accordance with the design of the sine wave engravings in the generator discs.
This section consists from left to right of a power supply, volume and swell pedals, power amp and solid-state amplifier (installed as a replacement for the original valve amplifier).
Sadly many Compton Electrones have been replaced by digital alternatives since their original installation. As such it is now difficult to find fully functional examples that remain in regular use today. It is also becoming increasingly difficult to find service engineers who are specifically familiar with the intricacies of the instrument.
Please use the following link to view the full set of photographs of the Compton 357:
Please use the following link to hear a recording of the photographed Compton 357. No stops were engaged when the recording was produced:
Sources:
Banton, H. (2015). MAKIN ORGANS HISTORY 1972 – 1992, Retrieved from
Bourne, L. (1935). Electrical musical instrument, US1996669A, viewed 01 December 2018, Retrieved from https://patents.google.com/patent/US1996669A/en?inventor=Bourn+Leslie+Edwin+Alexander&sort=old
Bourne, L. (1936). Electrical music instrument, US2032044A, viewed 01 December 2018, Retrieved from https://patents.google.com/patent/US2032044A/en?inventor=Bourn+Leslie+Edwin+Alexander&sort=old
Curtis, S. (2010). Compton Electric Organs, Retrieved from http://www.stancurtis.com/compton.htm
Electrokinetica. (2018). Introducing the Compton Electrone - the definitive British electric organ, Retrieved from http://www.electrokinetica.org/d8/1/index.php
Electrokinetica. (2018). How it works: The electrostatic generator. Retrieved from http://www.electrokinetica.org/d8/2/index.php
Electrokinetica. (2018). Introduction to the 1950s Electrones, Retrieved from
Electrokinetica. (2018). Model 357, Retrieved from http://www.electrokinetica.org/d8/4/2.php
Lawton, C. (2013). A BRIEF HISTORY OF THE JOHN COMPTON ORGAN COMPANY LTD, Retrieved from