We are working through the description of the instrument that CB Fisk is constructing for us: “a 3 manual tracker instrument of 39 stops in an eclectic tonal style.” If you have been following along, you can now explain to your neighbor or anyone else what a manual is and what tracker action is. Let's talk about those 39 stops now.
A stop is a group of pipes, one for each note or pitch on the keyboard. Even though each pipe is a different pitch, all of the pipes in the group will share a distinctive sound. When you look online at our specification: http://www.cbfisk.com/sites/default/files/instruments/specifications/153_spec.pdf you'll see stops numbered 1 to 39. When Grace is installed in our sanctuary, she will have 39 knobs with these names on them. The stop knobs, when pulled out, will allow air to that group of pipes. The organist will choose one solo stop or a group of stops to sound together.
There are four families of sounds: principal, flute, string and reed. Stops of each family are found in each division of the organ. The main sound of the organ is the principal family. It is a strong, clear sound. The flutes are lighter and gentler. The strings have a skinny sound because they are skinnier pipes. The principal, flute and string pipes are all flue pipes and produce sound in basically the same way. The reed pipes actually have a vibrating reed that puts the air in motion within the pipe. Some of the reeds that Grace will have are a bright solo trumpet, a trumpet that gets along well with others, a round, woody clarinet sound, a plaintive oboe and a big pedal reed that will be heard rumbling under the congregational hymns.
If you go back to that stoplist, you'll notice that there are numbers after the stop names. The stops that say 8' will be the same pitch as the piano. Middle C on the piano will be the same as middle C on the organ. It is designated 8' because the lowest pipe in that rank will be around 8 foot tall. Some of the stops say 4'. That rank will be an octave higher than piano pitch and the lowest pipe will be around 4 feet tall. A couple of the ranks say 2'. Those will be two octaves higher than piano pitch and guess what – the lowest pipe will be around 2 feet tall. The 16' and 32' will be one octave and two octaves lower than piano pitch respectively. The pipes that we will see on the front of Grace will be the Principal 16' so the longest one will be about 16 foot tall. So far we have talked about whole numbers. When you play a C you get a C, maybe higher or lower but still a C.
Some of the stop names have numbers with fractions behind them. These are mutations. When you play middle C with a 2-2/3 stop pulled, you get the G an octave and a fifth above middle C. Weird, huh? You wouldn't use that stop all by itself, but would combine it with other stops to make a beautiful solo sound. We'll save the discussion on harmonics for another day, but it works somewhat magically. (Unless you know something about physics, then it's physics.)
The mixtures have Roman numerals. When you play one note on the keyboard, you get more than one pipe speaking at various really high pitches. I am of course skipping a bunch of details that would help you understand this better; but for now let's just say – the mixture is used in combination with other stops, adding a crowning sparkle. Grace has a tiara!
Grace has 39 stops with distinctive voices, ready to do solos and work with others. Be like Grace. Are you an outgoing principal with a clear strong voice and bold action? Or are you a flute or string providing the harmony in the background with beautiful things to say? If you want to be a reed you might relish opportunities for public speaking, or be the one who adds spice to a group, or the voice of sorrow or even silly jokes. Like Grace, we have many distinctive voices. Let the music continue!