ENHARMONIC

in the system of equal temperament tuning used on keyboard instruments, two tones or intervals that sound the same but are notated differentlyfor example, c and d (enharmonic tones) or cf and cg (enharmonic intervals). The different notations indicate the key to which the tone or interval belongs. Enharmonic tones and intervals often serve as pivots in modulation (change of key). In earlier systems of tuning, such as just intonation and mean-tone tuning, the pitch of enharmonic tones was not identical; c then sounded slightly lower than d by about one-fifth of a tone. While the piano, harpsichord, and other fixed-pitch, equally tempered instruments cannot maintain this distinction, singers and violinists frequently do. Enharmonic in ancient Greek music referred to the tetrachord, or four-note series, containing intervals of less than a semitone.