The Basic Concepts
The Loche organ is designed to be naturally musical. This means simply that the sounds are pleasant to the ears, and it brings joy to the player and the listener.
To acheive this we borrow some basic concepts from pipe organs and symphonies.
1Just as a pipe organ has a multitude of sound sources that cause the sounds to mix acoustically, the Loche organ does likewise. There are 44 distinct output channels, each with its own power amplifier and speaker, scattered around the room. Stops that are likely to be used together in ensemble speak through separate speakers.
2Just as a pipe organ is never exactly in tune with itself, the Loche organ employs pitch sources that are not locked to each other. Therefore, there are more than 1100 individual separately-tuned oscillators that generate the pitches that are used in the Loche organ.
3To further enhance the concept that pitches slightly detuned from each other improve the quality of sound by producing warmth and fullness (like a violin section in an orchestra), most stops at 8 pitch have a slightly detuned celeste sound available that can be sent through a separate speaker to be mixed acoustically. Furthermore, since the organ has 4' stops on each of the three manuals and 2' stops on 2 manuals, the 61 notes of these pitches are purposefully but carefully detuned slightly from each other on a manual-to-manual basis. The result is sound that is warmer and fuller than it would be if everything was locked in tune.
Sixty-one separate oscillators are needed for each stop pitch that exists on a manual. The Great manual has stop pitches of 8, 4 2 2/3, 2, 1 1/3, and 1. Since the 8 pitch also has a celeste rank, the Great manual has 7 ranks of oscillators with 61 oscillators needed for each rank. Thats a total of 427 oscillators.
Likewise, the Swell division has stop pitches of 16, 8, 4, and 1 3/5, for a total of 5 ranks (including a celeste rank) and 305 oscillators.
The Choir division has stop pitches of 8, 4, and 2, for a total of 4 ranks and 244 oscillators.
The Pedal division needs 32 oscillators per rank. The stop pitches needed are 32, 16, 8, 5 1/3, and 4, for a total of 5 ranks and 160 oscillators. (The Pedal division does not use a celeste rank.) The point of reciting all these numbers is to get to an exact count of the oscillators: 427 + 305 + 244 + 160 = 1136.
Oscillators are turned on when a key is pressed. Which oscillators? The oscillators that generate all the possibly needed pitches for that note are turned on. Therefore, pressing a key on the Great manual turns on 7 oscillators (assuming no couplers are operated). Pressing a key on the Swell manual turns on 5 oscillators, and on the Choir pressing a key turns on 4 oscillators. Playing a Pedal note turns on 5 oscillators (again assuming no couplers are operated).
The volume level of a stop is determined by the DC voltage level applied to the oscillators. These DC voltages are controlled by the single volume-control pedal (called a Swell pedal).
When an oscillator is turned on it generates two kinds of waveforms: (1) a sine wave that contains essentially no harmonics other than the first harmonic, and (2) a "rectified" waveform that is rich in harmonics. These waveforms are summed together with other waveforms generated by other keys being played at the same time and sent to filter cards that filter out unwanted harmonics and perhaps emphasize others. There is one filter card for each stop and these filter cards produce waveforms that represent the needed stop sounds. Operating a stop switch on the console operates a relay on the output of a filter card which causes the waveform to be passed on to one or more power amplifiers and speakers.
Amplifiers and speakers
Power amplifiers and speakers are located in three separate areas: in the lofts on both sides of the chancel and in the balcony. The purpose of this arrangement is to spread the sound around the sanctuary. The acoustics, like in so many other gathering spaces, are not overly live when the room is full of people. When I run for President, my platform to save the world will be: "Carpet bedrooms not churches."