tonality, in music, quality by which all tones of a composition are heard in relation to a central tone called the keynote or tonic. In music that has harmony the terms key and tonality are practically synonymous, embracing a hierarchy of constituent chords, and a hierarchy of related keys. Some relationship to a tonic is characteristic of all music except that in which it is deliberately avoided (see atonality and serial music). The term tonality is also used in contrast to modality (see mode).

Organization of music around a single pitch; more specifically, the Western system of keys that grew out of the modal music of the Renaissance in the 17th century. The term is often used to refer to the network of relationships implicit in the seven principal tones of a given key, each of which has the potential to become the tonic temporarily by means of modulation, whereby a new network of relationships arises. Because of its capacity to extend pitch relationships to remote lengths in an audibly comprehensible way, the tonal system permits the composition of music of great complexity.

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