Tierce, i.e., Tiers, third.

  1. A name given to the interval of the Third, whether Major or Minor.
  2. The fourth of the series of natural harmonics, being the Major Third in the third octave above the ground tone or prime; its vibrations are five times as numerous as those of its prime.
  3. An open metal organ stop of the same pitch as the similarly named harmonic, i.e., if the note CC is held down and the Tierce-stop drawn, the E above middle C will be heard. That such a stop can only be used in combination with certain other harmonics, and then but sparingly, will be evident when it is remembered that if C, E, and G be held down there will be heard at the same time G sharp and B. Hence, the Tierce when found in a modern organ is generally incorporated as a rank of the Sesquialtera or Mixture, in which case it is of course combined with other harmonics, its near relations. Most organ builders, however, altogether exclude it. A serious difficulty is now met with, if a Tierce be introduced; it is this – modern organs are tuned to ‘equal temperament,’ whereas the Tierce (whether a separate stop or a rank) certainly ought to be tuned to its prime in ‘just intonation,’ in which case tempered and natural thirds would be heard simultaneously when the Tierce is used. Much difference of opinion existed as to the utility or effect of this stop.