Microtonal music
Music with intervals smaller than a semitone, such as quarter tones or sixth tones.
What it means
Microtonal music uses intervals smaller than the semitone, the smallest step of the equal-tempered European scale. These include quarter tones, sixth tones or finer divisions of the octave. Such notes lie between the keys of a normally tuned piano and therefore cannot be played on it.
In the notation
For quarter tones there are special accidentals: a half sharp raises a note by a quarter tone, a flat with a stroke through it or a reversed flat lowers it by a quarter tone. There is no universally accepted notation; composers usually explain their signs in the preface of the score.
Musical use
Microtonal intervals are a matter of course in many non-European musical cultures, for instance in the Arabic maqamat, in Turkish music and in Indian systems. In European art music of the 20th century they were explored by composers such as Alois Hába, who wrote quarter-tone music, Julián Carrillo and Ivan Wyschnegradsky. Harry Partch developed his own tonal system with 43 notes to the octave and built his own instruments for it.
Microtonal music should be distinguished from mistuning and fluctuations of intonation: its small intervals are deliberately planned and a fixed part of the tonal system.
Performance practice
When you sing or play microtonal intervals on a string instrument, first practise them against a drone. Listen to the beating between the notes and tune carefully, since the distances are smaller than your ear is used to.