Electronic organs - circuits, experiences and interests

[Lucien Nunes]

Even most of the acoustic pipe organs have keyboard & stop electrical switches, solenoid electric valves at the bottom of each pipe

This thread is mainly going to be about electronic organs, but I will touch on the subject of electric action of pipe organs for a moment as it's been raised. Historically, pipe organ action was purely mechanical - pressing the keys opened wind pallets, drawing stops opened the sliders. Indeed, purely mechanical 'tracker' actions are still used, and favoured for some styles of organ and playing. In the 19th century, tubular pneumatic action enabled the console to be remote from the windchests and allowed for various control functionality. But it was the coming of electric action in the 1880s, and especially from 1900 onwards, that enabled many new functions and developments. One of the early proponents of this fusion of electromechanics and organs was Robert Hope-Jones, younger brother of Frank (of Synchronome fame) who did the same with electromechanics and clocks. The cinema organ, in particular, owes much to Hope-Jones's efforts to use electricity to elicit more versatility from a given number of pipes.

Later on in the thread, I will give you a tour of the extensive electric workings of a really large, complex pipe organ. I am privileged to be responsible for maintaining the electrics of the 1937 Southampton Guildhall Compton, one of Compton's masterpieces of unique design that fulfils the roles of both classical and entertainment playing and has about the most diverse tonal palette of any in existence. To offer the organist the most suitable facilities and performance environment for any style of music, it has two fully equipped 4-manual consoles of completely different design, layout and stoplist, both controlling the same pipework; one optimised for entertainment and light music, the other for classical repertoire. Behind this show of mutifarious flexibility is a substantial organ of 50 ranks, many highly extended, voiced to a high standard and also equipped with an original 'Melotone' electronic tone generator.

Unlike many organs, it has not been modified, expanded, contracted, tinkered with, revoiced, relocated, re-imagined... or any of the many things that often befall organs as fads come and go and musical opinions change. It is exactly as Compton built it in 1937, with all of its original pipework and actions. On the electrical side, the only modernisation done has been to replace a few hundred feet of perished rubber wiring. Thankfully, rubber insulation was only used on about sixty runs from the windchest common negative terminals to the main distribution blocks. Most of the wiring is cotton covered and in perfect original condition.

So, some electrical stats to make you sit up and think. These numbers are top-of-head and approximate:

3,650 pipes each with its own electromagnetic armature valve (called a 'chest magnet' in organ parlance.)
7,000 electromagnets / solenoids total, including relay coils, chest magnets, stopkey units etc.
552 keyboard keys each making up to six contacts.
> 50,000 contacts total including relays, matrix relays (multiplier-adders), memory units etc. Some relays up to 61 poles each.
>100 miles DCC (cotton covered) wire.
4.5 kilobits of non-volatile electromechanical binary memory for combination piston settings.
Action powered at 18V from motor-driven dynamo, 100A continuous output, 250A peak.
Audio output from 'Melotone' electronic tone generator section via 4x PX25 and dual-driver Vitavox horn.

Enough pipe organ stuff already, tomorrow I'll pick an electronic and tell you about it.