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).