A manual of an organ typically has 61 keys, or just over five octaves. That means recording 61 samples per stop, and that quickly adds up, with some organs having upwards of sixty stops (like St. James Cathedral’s Organ).
That said, I’m lucky enough to be recording the beautiful organ at Our Lady of Sorrows in West Toronto, which has a much smaller selection, with only two manuals and a pedalboard, totaling 27 combined stops. Still that works out to approximately 1400 samples, so I still have to narrow down what exactly to record.
To narrow down my selection, I had to understand exactly how the nomenclature of organ stops works. There are five types of stops: Principal, Flute, String, Reed, and Hybrid.
Principal stops are the “classic” sound of the organ, where it’s not trying to imitate the sound of another instrument. These are the stops which I will focus most of my effort on.
Flute stops are, not surprisingly, made to imitate the timbre of flutes, and similar instruments, like the piccolo.
String stops again are fairly straight forward, trying to imitate the sound of classical string instruments (although I can’t help but imagine how a modern “electric guitar” stop would sound). Our Lady of Sorrows’ Organ doesn’t have too many of these, so I’ve essential cut them out.
Reed Stops are a broader category, imitating brass, woodwinds, and even the human voice. These stops also use reed pipes as opposed to flue pipes, where the wind is pushed through past a brass reed, which vibrates to create the sounds. Whereas flue pipes rely solely on the vibration of air.
and finally, Hybrid stops, are stops which try to imitate the combined sound of two types of stops, such as principal and flute, or string and reed, and so on.
From here, each stop is labeled with a number. This number signifies the length of the longest pipe in a given rank (with some exceptions), and the longer a pipe is the lower the pitch of that pipe. 8′ stops are what are known as the “native pitch”, or “unison”, with each halving of length resulting in a doubling of pitch (4′ is an octave higher than 8′ and 16′ is an octave lower than 8′). There are also “mutations” which play at non-unison intervals. For example, a 2 2/3′ stop will play at the 12th (or an octave of the 4th) of an 8′ pipe.
The organ at Our Lady of Sorrows has two manuals, the Great Organ and the Positiv. This is a bit different from most two manual organs, which consist of a Great and a Swell .
The Great Organ contains the principle sounds of the organ as well as occasionally housing a solo-instrument stop such as the trumpet.
While the Positiv contains more solo oriented sounds.
The Pedals are typically meant to give the organ a bass-frequency foundation, although occasionally also can be played for solo-melodies.
Luckily for me, neither these manuals nor the pedals use swell boxes, which means that there will be no need to account for variation in note velocities.
The Final List
With this knowledge, and the handy-dandy stop-list of Our Lady of Sorrows’ Organ, I’ve come up with a plan to record 8 stops on the manuals, and 3 stops on the pedals, for a total of 582 samples.
The Great Organ: Principal 8, Octave 4, Nasat 2-2/3, Superoctave 2, and Mixture V 1-1/3
The Positiv: Salicional 8, Gemshorn 2, Sifflöte 1
Pedal Board: Oktavbass 8 , Choralbass 4, Nachthorn 2