Introducing the Relay – The “Brain” of the Theatre Pipe Organ

Experience the sound of the Theatre Pipe Organ

We know that all of that beautiful music is able to come out of a Theatre Pipe Organ because a large turbine, called a “blower” supplies wind pressure to the instrument. The wind travels up metal or plastic wind lines, goes through pressure regulators, reservoirs, and tremulants, and provides wind pressure to the chests upon which sit all the different ranks of organ pipes.  We also know that there is a valve under each pipe in each chest.  When the valve opens, the wind rushes up through the pipe and it sounds.  But, how do these hundreds of valves receive their instructions to open when the organist wants to play their note in their rank of pipes?

The first organs built, long ago, solved that problem very simply. The organ keys were physically connected to the pipe valves.  These “tracker” organs obviously had limitations.  The console had to be situated right next to the pipes, and flexibility was limited by physical space constraints.

Then the concept of the relay came along. Electro-pneumatic action, controlled by electricity and wind could “relay” instructions to the pipe valves, and the console keys no longer had to be physically connected to the pipes. Perfected for the Theatre Pipe Organ by Robert Hope Jones, electro-pneumatic action utilized electrically activated solenoids to open each valve, and low voltage electrical contacts under each key and stop tab to send the commands to the air valves. These relays contained hundreds of switches and miles of wiring.

For example, let’s assume we have a 3 manual instrument. Sixty-one keys on each manual times 3 equals 183 switches, plus 32 pedal notes equals 215 switches and that is just to play one rank at 8’ unison pitch! It is no wonder that these relays were cumbersome. Stacks and stacks of switches were utilized. Seeing photographs of 1920’s era theatre pipe organ relays reminds one of the old time telephone switching centers with their banks and banks of switches.

1920s Era Relay Switch Racks

While electro-pneumatic action disconnected the console keys from the pipes, it was still cumbersome with masses of wires running from the back of the console to the relay switches. The sum of these wires could result in a cable as much as 8” or more in diameter!

Enter electronics. The commercialization of the transistor in the late 1950’s revolutionized the use of electricity in switching. The development of the computer in recent decades advanced the process tremendously more.

We use a numbering system based on 10 digits in our daily lives, but many computers use the binary numbering system which is based on only two digits: 0 (zero) and 1 (one). The absence of electrical current represents “zero”, and the presence represents “one” ie, a simple switch, “off” or “on”. Thus organ relays are natural applications for the computer. Add to the mix the development of integrated circuits or “computer chips”, and switch miniaturization has advanced even more dramatically.

Also tremendously helpful has been the development of multiplexing. Multiple streams of data are simultaneously transmitted down a wire, single file, and reassembled at the other end. This has enabled the mobility of consoles, since that huge mass of wiring coming out the back can be replaced by a tiny multiplexing wire.

Is it any wonder that many 1920’s electro-pneumatic relays have ended up on the junk pile in favor of modern computerized versions?

Today’s computerized organ relays are truly marvels. They no longer just “relay” the message, making the proper pipe sound when a key and stop tab is pressed. They can transpose your piece of music (You can play the music in one musical key and the pipes play it in another). They allow organists to enter hundreds of preset combination pistons. They allow musicians to design their own crescendo (adding ranks to the sound as the crescendo pedal is depressed), and sforzando (“full” organ) combinations.

They also feature record/playback. The performance is captured by the computer, and it can be duplicated (by the computer playing the organ) at any time. Musicians can now play back their performance on the organ, while accompanying themselves on another instrument such as a piano. Some owners of residence theatre pipe organs utilize this feature to record the performances of visiting professional artists. They then can have their instrument play back the exact same music at any time with no performer present.

Vintage thus meets modern. The computerized relay has become the “brain” of many of today’s Theatre Pipe Organ installations.