A Dictionary of Music and Musicians/Harmonic Stops
HARMONIC STOPS are organ stops, the upper pipes of which do not produce the sound that would be expected, having regard to their length, but the octave to that sound. They have been known in Germany for nearly two hundred years. The 'violoncello, 8 feet pitch' on the Pedal organ at Weingarten, made in the first half of last century, is in reality 16 feet in length, of tin, and 3½ inches in diameter.Harmonic stops have in recent years come into great favour, in the first instance through the careful and successful experiments of the eminent French builder, M. Cavaillé-Coll, of Paris. Guided by the fact that performers upon wind instruments exercise a greater pressure of wind for the production of the higher notes than the lower, the above ingenious builders applied the same principle to some of their organ registers, with the most excellent result. In this manner they produced the stops—most of which have been naturalised in England—called 'Flute Harmonique, 8 pieds,' 'Flute Octaviante, 4 pieds,' 'Trompette Harmonique, 8 pieds,' etc. At first only a few experimental pipes were made to test the soundness of the theory, for the resistance presented to the finger by the highly compressed air was so excessive as to prevent their adoption in practice; but the invention of the Pneumatic lever removed this objection, and Harmonic Stops and the Pneumatic attachment were introduced together for the first time, in Cavaillés fine organ in the abbey church of St. Denis, near Paris, finished in 1841. Very effective Harmonic Flutes, though naturally less powerful, are frequently voiced upon a wind of the ordinary strength when there is a copious supply of it.
[ E. J. H. ]