microtonal

Microtonal refers to musical tunings, scales, and compositions that use intervals smaller than the conventional semitone of the Western 12-tone equal temperament, or scales that divide the octave into more than 12 parts. In practice, microtonality encompasses systems that do not fit the standard 12-tone division, including both non-equal temperaments and very small steps such as quarter tones.

Common approaches include equal divisions of the octave into 19, 24, 31, or 53 parts (19-ET, 24-ET, 31-ET, 53-ET); just intonation based on simple frequency ratios; and non-equal temperaments designed for particular musical aims. Many non-Western traditions use microtones: Indian classical music employs shrutis within an octave; Arabic and Persian maqams incorporate microtonal intervals; Indonesian gamelan traditions utilize scales such as slendro and pelog with smaller and uneven steps. In Western art music, microtonality emerged in the 20th century through composers such as Harry Partch, Alois Hába, and Ivan Wyschnegradsky, later expanded by electronic and computer-based tuning.

Notation and performance of microtonal music often require new accidentals or scale-degree markings, specialized instruments, or electronic sound sources. Some keyboards, synthesizers, and fretted instruments are built or retuned to allow microtonal pitches; others use software to map arbitrary tunings to MIDI or digital audio.

Microtonality broadens expressive possibilities and poses challenges for standardization, pedagogy, and audience familiarity, but remains an active area in experimental, contemporary classical, and some popular music practices.