Electronic organs - circuits, experiences and interests

[Radio Fixer]

It is really amazing the complication of these organs. Never come across any apart from being a kid and going to a cinema that had one: I have loved the sound ever since.

I had no idea what electrostatic tone generation was but found this very good explanation: https://www.jayharrisonaudio.co.uk/post/...o-of-three
From there I went to You Tube where there are a number of videos.

Thanks Lucien. Following on with interest.

Gary

[Lucien Nunes]

found this very good explanation: https://www.jayharrisonaudio.co.uk/post/...o-of-three

There are a couple of minor errors there. It references my own site but has also borrowed one of my pics. My original blurb is here and on associated pages:
http://www.electrokinetica.org/d8/2/index.php

It is really amazing the complication of these organs

You haven't seen some of the most complicated bits yet. The underlying reason is that the pipe organ has at its core a very large number of independent and independently-controllable sound sources. Electronic emulations therefore also need a large number of independent sources and the means to bring them all under the control of two hands and two feet.

A few years ago I did a write-up on another forum under the title '193 valves in 5 days' about a quick turnaround of a Miller organ from the early 1960s based on independent valve oscillators. Between the 4 ranks there are 29 octaves (= 348) of generators each using half an ECC82, each producing two waveforms, for a total of 696 tone signals. There were a few larger examples but this was pushing the limit of practicality at the time. Depending on model, Hammond tonewheel generators produce between 82 and 96 tones. The small Compton generators produce 84 tones, larger models usually either 252 or 324, although not all independent in phase as are the Miller's oscillators, a point we'll return to later.

Very convenient wiring for tracing Lucien. Blue goes to blue, to blue :-) I hope they are number coded.

As with most pipe-organ wiring, extensive use is made of strict lacing of the wiring looms so that every core is tied out in numerical order. Identification is then by position in the loom rather than colour or number. Historically the wire was double cotton-covered and all white. Compton were very early adopters of PVC insulation, for example on the polarising circuits of Electrone generators where high insulation resistance is desirable. In these they usually wired C's in a contrasting colour for speed of tracing, e.g. if you want to find middle G# you count along 3 C's and 8 more wires. The 18V DC action wiring was often still DCC-insulated due to the much smaller radial thickness leading to more compact looms.

3 Pics from the Compton Draper organ:

Cut cable loom. This is one disadvantage of not using colour codes. This should never have been cut, it's the main loom linking the console to the generator rack in the Draper organ, about 275 cores. This was done before I bought the organ, as the people moving it wanted to detach the generators to make it lighter. They assumed I would be junking them and converting it to a digital, instead of restoring it (why would you do that?). Had they been disconnected at the test board, it would have been simply a matter of reconnecting as the lacing would have preserved the identity of every wire.

Another pic shows 18V action wiring in DCC 26SWG on the back of the combination setter board, where there is one wire per stop per piston.

Then we see the back of a 61-note 13-bar key relay. Note the DCC loom for the 18V magnet wiring along the top, which is a small part of the large loom from the console to the generator rack. Then in the yellow polarising feed loom to the generators the C's are in blue, and on the white relay diagonal crosswiring itself the C's are red.

[radioman]

There is a Compton cinema organ at the Summerlee Museum, Coatbridge.
https://www.culturenlmuseums.co.uk/SIModes/Detail/8243
When I visited about four years ago, they were looking for crowdfunding money to help restore it.
Mentioned on the sheet I picked up, was the 'melotone' unit that this particular organ once had and which uses electrostatic principles to generate sound.
I don't think they ever managed to restore this unit to the organ unfortunately.

Andy

[Lucien Nunes]

The Melotone was Compton's first electrostatic product to reach production in 1935. It was an add-in for a cinema organ that was not a complete instrument in itself, but added some extra tone colours, especially useful on smaller organs. Also found on large instruments as it could make sounds that pipes could not. Summerlee has one of the popular small 6 rank + Melo Comptons, but IIRC (and I might have this completely wrong, I should really check) the Melo went missing during refurbishment works on the building and organ. I seem to remember thinking at the time, that someone probably assumed it was a piece of old PA / cinema sound equipment and threw it in the skip. It wouldn't be an isolated case. More recently, during the refurbishment of the Odeon Leicester Square, the building contractors ripped out not only the Melotone's loudspeakers and wiring but the organ console lift controls and switchgear etc, assuming all old electrical equipment to be redundant. Donald MacKenzie went to re-commission the organ and found no power to the blower and a dismantled lift. It took him a while to get that lot sorted out.

Of the 74 Melotones made, around 15 were operational the last time I had a count-up. One has been living with me for a while, from the ABC Plymouth organ that is in store. While it was in the workshop, we had the rare sight of two side-by-side while we were servicing the one for Pipes in the Peaks. I am supposed to look after the one at Southampton, but we get so little access to the venue and there is always so much to do, that it doesn't get as much attention as it should.

One of the interesting quirks of the tone generators of the original Melotone, is that it is not quite in tune with itself. This is due to the original configuration of encoding four complete octaves in each generator, where adjacent semitones cannot have exactly correct frequency ratios as there must be an integer number of cycles of each waveform. By the launch of the Theatrone in 1938, they had progressed to using 12 separate smaller generators, one for each semitone in the octave. But, somewhere between these two was the prototype self-contained electrostatic organ that debuted at their Acton works in 1935. It appeared in Wireless World on 24th May of that year, where we see a tantalising glimpse of an extended Melotone cabinet with three generators instead of two, and an extra matrix relay.

Pics - The Compton Melotone series 3. Earlier versions were in metal cabinets, one for the generator and one for the amplifier.

[Raditechman]

When I went to Saturday morning pictures at Twickenham Odeon Ena Baga used to play the Compton organ which I believe had a Melotone fitted.
After that cinema closed I think part or all of the Meltone went to the Odeon Leicester Square Compton

John

[Lucien Nunes]

I don't know the history of the Odeon Twickenham organ but the cinema was opened before the Melotone was launched. Could it have been added? I think the organ was augmented by one or two ranks later on so it's possible. One to investigate.

Did anyone notice the DA30s in the pic of the two Melos? The earlier amplifiers built by Ferranti for the series 1 and 2, used two pairs of PX25s as two separate channels. But the Series 3 adopted the DA30, introduced in 1935, as one pair of valves could deliver 45W in AB1, almost the same as the two pairs of PX25s. Naturally they are transformer-coupled (intervalve transformer to right of central output transformer) and the driver is parallel fed by the choke above it. Bias comes from the selenium stick somewhat hidden below the mains transformer bottom left.

[Hartley118]

Back in the late 1960s when I was involved with theatre acoustics, I recall a visit to the Davenport Theatre in Stockport http://cinematreasures.org/theaters/1832 .  The manager was receiving complaints of an echo in some seats.  I went along with an organist friend of mine who was keen to play the Compton, which in turn gave a great account of itself.  We had the run of the place so that  I could record gunshots for later lab analysis. Interestingly, much of the technical equipment in the projection room was original from its installation in 1937 - a museum piece frozen in time with only the projectors and sound system having been updated for widescreen presentations. Even the monitor speaker used with optical tracks was the original Western Electric 'curly' horn complete with its Western Electric driver . The original Holophane lighting effects equipment directed at the reflective proscenium surround was pretty impressive kit, presumably used as a colourful accompaniment to the organ performance.

I remember seeing the Melotone horn speakers projecting from under the stage, but don't recall hearing any sound from them.  I wish I'd known more then about the Melotone to have investigated  more thoroughly.  Audience members in the front stalls would have heard more than their fair share from the Melotone speakers!  It's good to know that the organ is now in the care of the Lancastrian Theatre Organ Trust.  I came across a 1989 recording on Youtube by Doreen Chadwick  https://www.youtube.com/watch?v=txMHlx1W1VM and a further episode showing photos of the theatre  including its sad demolition, all accompanied by the Compton played by Joyce Alldred https://www.youtube.com/watch?v=9oYtqfqNnQA .  Is it possible from the recordings to hear the Melotone?

The organ is now thankfully in the care of the Lancastrian Theatre Organ Trust. A recording in its current home (played by Kevin Morgan) is at https://www.youtube.com/watch?v=x0G3i8Z4gzc . I don't know whether the Melotone moved with it.

Oh - and the acoustics. The echo was due to reflections focused from the curved back wall and balcony front.  I recommended absorbent treatment, but the final solution was a pretty comprehensive remodelling which included converting the restaurant into a second screen. The final final solution of course has been demolition.

Martin

[Lucien Nunes]

Whenever a remarkable coincidence occurs, I always remind myself of all the possible coincidences that didn't. I have never written about the Davenport and its 3/6+M organ until a few hours ago, when I mentioned on a FB post that it was the venue for a demonstration of the 'New Compton-Makin Theatrone' in June 1975, at which Joyce Alldred played the theatre's own organ and Doreen Chadwick played the New Theatrone. The programme of that event specifically states that the (series 2) Melotone was already inoperative / decommissioned, and indeed I don't hear it on the video. It was rescued with the organ and is at the Heritage Centre, awaiting restoration. Doreen Chadwick started out on the Theatrone of the Rex Aberdare, picture below.

Seeing as we have become deeply involved in the electrostatic instruments of the Compton firm, I should provide a glossary of their slightly convoluted usage of trade names ending in '-one':

Electrone (1): The name of the electrostatic tone generation system that it seems Compton originally intended to apply to any instrument using the system.
Electrone (2): The name given to all self-contained electrostatic church and classical-style organs, and some post-war entertainment organs, from 1938 to 1971.
Theatrone: The first self-contained entertainment organs, intended for use instead of a cinema pipe organ, of which approximately 12 were made before WW2 and six after.
Melotone (1): Pre-WW2, the add-in electronic division for the cinema pipe organ, not a complete instrument in itself, of which 74 were made between 1935 and 1939.
Melotone (2): The stop-name of the 'virtual rank' of electronically-produced 'prime' tones at 8', 4', 2 2/3' and 2', on a cinema organ or Theatrone.
Melotone (3): Post-WW2, another name for the model 352 entertainment organ, and its vanishingly rare spinoffs the 'Super Melotone' and 'Melotone De Luxe.'
Electone (without an r): Not used by Compton; Yamaha's name for their popular range of electronic organs.

It is my understanding that the original intention was for the tone generator equipment, and the complete organ based on it, to be called the Electrone. Amongst the various stops of different tone colours that it produced, such as the Krummhorn and the Cor Anglais, the 'virtual rank' of stops of pure tones direct from the Electrone generators were named Melotone (with the tab short-form of MELO). Thus, the Theatrone organ could have Melotone stops, as could a cinema organ fitted with an Electrone unit. However, because the stop name 'Melotone' was the one used and referred to by cinema organists, the name 'Melotone' soon came to mean the machine itself, and that is how it is universally known today.

Aside from the rather complicated double-meanings that arose, I think the three names are excellent for their purposes. 'Electrone' combines the completely relevant and then modern-sounding 'electron' with the 'one' of 'tone'; 'Theatrone' changes only four letters and is clearly of the same family, yet makes an immediate connection with entertainment and the cinema; and 'Melotone' is similar enough in form to be immediately associated while also being a perfect homophone of 'mellow tone' which exactly describes the sound. I wish I knew who coined them.

Pic: Doreen Chadwick at the Rex Aberdare Theatrone (One of the few that survives today)

[ppppenguin]

Lucien, you have posted here and elsewhere about organs, espcially Compton instruments where you have a lot of specialistand probably unique knowledge. These posts, and your Electrokinetica/MEET website have recorded some of this knowledge but do you have any plans for further documentation?

This is part of a more general question of the loss of knowledge. When the old (and not so old) timers have gone, much of what they know often goes with them. Forums like this play an important role in reducing that loss. The term used by historians is "tacit knowledge". The sort that isn't in the books. The sort that was traditionally passed from master to apprentice in an unbroken chain. Whether it's about Compton organs, image orthicon TV cameras, mercury arc rectifiers, videotape recorders or any other now-obsolete technology.

[Mike Watterson]

Even not obsolete tech. There is also proprietary info only in a company, but companies go bust.
Try assembling detailed info (not just general principles) to cut silicon boules into wafers that can be processed. Imagine you haave a furnace for each doping. Try documenting complete step by step to make a 741 op-amp or a 4000 series logic gate or a power FET (hint: they are multiple parallel FETs on one chip).

Or how would you make a halogen lamp or florescent tube? The broad explanations are easy, a manufacturing step by step recipe is harder.

Some things seem easier, like pre-1970s piston engine car. However if you were working from scratch rather than buying parts how do you make:
Triplex glass
Piston rings
brake shoes
metal pipes for brakes
rubber / plastic pipes
sparkplugs
the light bulbs
wire to wind starter motor, generator and ignition coil
Tyres

Or if you can't buy aluminium and steel and scrap is unavailable how do you really make those from scratch?

A working copy of wikipedia would be no use after an apocalypse because by design it doesn't have step by step "how to". Wikihow isn't part of Wikipedia, but it's not much use on the majority of tech from scratch. https://www.wikihow.com/Main-Page