The Harmonic Series

1 3/5' PITCH (the fifth partial)

As the string continues to vibrate in this complex way, it also vibrates in fourths, producing the seventeenth, the E two octaves and a major third above tenor C. This is the fifth partial or harmonic, and the fourth overtone.

If you were to play tenor C at the organ and pull a 1 3/5-foot stop only, you would hear the seventeenth, the E two octaves and a major third above tenor C.

1 3/5' stops are third-sounding stops; that is, they sound the note name a major third above the key being played.