Octave helpers extend the lower range of pipe organs when budgetary or space limitations prevent an organ maker from creating a full-range instrument. The term "octave helper" actually refers to a few specific practices in pipe design and in the combination of pipes to help the lower register of an organ sound more fully.
The Reasons for Octave Helper Use
Pipe organs generally have one pipe for every note. These instruments become large collections of pipes in order to provide the wide range of sounds and registers desired by an organ maker. Organ making and organ design can encounter limitations in the case of organs in churches that are centuries old. Sometimes there is not enough space for the very largest and lowest pipes. Other times the budget is simply lacking. An organ maker must either leave the lowest notes out completely or improvise a solution.
Solutions in Pipe Design to Create Artificial Lower Octaves
Organ makers eventually discovered that pipe alterations could create the artificial appearance of low notes without requiring the full height of a normal pipe. In the early 20th century, the organ maker William Haskell invented several designs that take pipes and suspend closed tubes within or over them. The result is a note one octave lower, thereby solving the problem of extending an organ's range while not having the space for the pipe.
Blending Pipe Sounds for Better Bass
The Haskell bass design proved effective in creating lower notes, but the sonic quality of the notes was erratic and not always trustworthy. Organ makers found that adding an additional pipe, usually one octave higher, would reinforce the weaker artificially created note. The added pipe would "help" the lower to create a full, musically useful sound.
Tricks in Physics of Sound to Simulate Octave Helpers
Octave helpers, either via pipe alteration or by addition of supplementary pipes, combine overtones to simulate lower notes. In the absence of octave helper pipes, an organist can actually play two lower notes to simulate a third "phantom" note even lower that the organ may lack. The overtones of any note begin with one octave, followed by a fifth and then a fourth. By playing a fourth extremely low on the organ, sympathetic vibrations can cause the octave underneath to appear, allowing the instrument to seem to have a lower and more impressive range.
- "The Organ, its History and Construction"; Edward J. Hopkins and Edward F. Rimbault; 1877
- "Harmonics and 'Cheats'"; Stephen Bicknell, Organ Historian, Designer and Consultant
- "Haskell Basses"; Encyclopedia of Organ Stops; 2003
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