Foundation stop
Organ stop that sounds the note c, or one of its octaves, on the key c (foundation stops, e.g. 8'/16').
What it means
A foundation stop is an organ stop that sounds the note c, or one of its octave notes, on the key c, that is, in octaves of the played note. Foundation stops include stops at 8ʼ and 16ʼ, which reproduce the played note at normal pitch or an octave lower, as well as 4ʼ and 2ʼ, which sound in higher octaves.
Musical use
Foundation stops form the basis of the organ sound, on which mutation and mixture stops build as overtones. Typical foundation stops are principal, gedackt, bourdon, and flute. An 8ʼ stop sounds at normal pitch because its longest pipe measures about 8 feet, roughly 2.4 metres; a 16ʼ stop sounds an octave lower, a 4ʼ stop an octave higher.
Foundation stops should be distinguished from mutation stops such as the fifth and tierce, which sound overtones outside the octave series, and from the mixture, which combines several pipes per key. The sound of foundation stops alone is calm and not very rich in overtones; only the upper-work stops give it brilliance.
Performance practice
For the basic sound of an organ, choose one or more foundation stops first and add overtone stops only as needed. Check the balance so that the higher stops do not cover the foundation.