The Harmonic Series

32' PITCH (two octaves below the fundamental)

Doubling AGAIN the length of the vibrating tenor-C string, resulting in a string FOUR TIMES that length, produces a pitch two octaves below tenor C.

If you were to play tenor C at the organ and pull a 32-foot stop only, you would hear the C two octaves below tenor C.

32' stops are octave-sounding stops; that is, they sound the note at some octave above or below the key being played.