CHAPTER XI.
TUNING.
Having described the improvements in pipes, we now consider how they are tuned, and the first thing we must notice is the introduction of equal temperament.
About fifty years ago most organs were so tuned that the player had to limit himself to certain key signatures if his music was to sound at all pleasant. Using excessive modulation or wandering into forbidden keys resulted in his striking some discordant interval, known as the "wolf." The writer remembers being present at a rehearsal of Handel's "Messiah" in St. George's Hall, Liverpool, Eng., in 1866, when the organ was tuned on the unequal temperament system, and there was a spirited discussion between the conductor and Mr. W. T. Best, who wanted the orchestra to play "Every Valley" in the key of E flat so as to be in better tune with the organ.
The modern keyboard is imperfect. One black key is made to serve, for instance, for D sharp and for E flat, whereas the two notes are in reality not identical.[1] To secure correct tuning and tone intervals throughout, forty-eight keys per octave are required, instead of the twelve now made to suffice.
In what is called the equal temperament system the attempt is made to divide the octave into twelve equal parts or semi-tones, thus rendering all keys alike. To do this it is necessary to slightly flatten all the fifths and sharpen the major thirds. The difference from just intonation is about one-fiftieth of a semi-tone. Although recommended and used by J. S. Bach, equal temperament was not introduced into English organs until 1852.
Much has been lost by adopting equal temperament, but more has been gained. To a sensitive ear, the sharp thirds and fourths, the flat fifths and other discordant intervals of our modern keyed instrument, are a constant source of pain; but the average organist has become so accustomed to the defect that he actually fails to notice it!
The change to equal temperament has on the other hand greatly increased the scope of the organ and has rendered possible the performance of all compositions and transcriptions regardless of key or modulation.
The tuning of an organ is seriously affected by the temperature of the surrounding air. Increased heat causes the air in the open pipes to expand and sound sharp contrasted with the stopped pipes through which the air cannot so freely circulate. The reeds are affected differently, the expansion of their tongues by heat causing them to flatten sufficiently to counteract the sharpening named above. Hence the importance of an equable temperature and the free circulation of air through swell-boxes, as described on page 59, ante.