Arabic music
Microtones in Arabic music

Unlike the tradition of Western music, Arabic music contains microtones, which are notes that lie between notes in the Western chromatic scale. While notes in the chromatic scale are separated by semitones (or half steps), notes in Arabic music can be separated by quarter tones. In some treatments of theory, the quarter tone scale or all twenty four tones should exist, but according to Yūsuf Shawqī (1969), fewer tones are used in practice.

Additionally, in 1932, at the Cairo Congress of Arab Music held in Cairo, Egypt—and attended by such Western luminaries as Béla Bartók and Henry George Farmer —experiments were done that determined conclusively that the notes in actual use differ substantially from an even-tempered 24-tone scale. Furthermore, the intonation of many of those notes differ slightly from region to region (Egypt, Turkey, Syria, Iraq).
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