1 In music, term used to indicate the scale from which the tonal material of a given composition is derived. To say, for example, that a composition is in the key of C major means that it uses as its basic tonal material the tones of that scale which is associated with C major, and that its harmony employs the chords built on the tones of that scale. C is then the keynote, and the C major triad, or the notes CEG, the tonic chord of the composition. In addition to the seven tones of the C major scale, however, the remaining five tones of the chromatic scale may appear as auxiliary tones, and chords may be borrowed from other keys. Modulation to another key may take place, but if there is a return to the original key the whole composition is said to be in the key of C. At the beginning of a composition, its key is usually indicated by a key signature (see musical notation). A term usually used synonymously with key is tonality. Absence of a feeling of key is called atonality. The concept of keynotes was developed gradually during the 16th and 17th cent. and its partial or total abandonment was a feature of the modernism of the early and mid-20th cent. Polytonality, the employment of two or more keys simultaneously, has been used by some 20th-century composers. 2 Also in music, in reference to musical instruments the term key refers to a lever depressed by the player's finger or, in the case of the pedal keyboard of the organ, the foot. In woodwind instruments the keys control covers on the holes that shorten the vibrating column of air. In brass winds they control the valves that lower the pitch of the instrument by lengthening the tube.
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