The modernArab tone system, or system ofmusical tuning, is based upon the theoretical division of theoctave into twenty-four equal divisions or24-tone equal temperament, the distance between each successivenote being aquarter tone (50cents). Eachtone has its own name not repeated in different octaves, unlike systems featuringoctave equivalency. The lowest tone is namedyakah and is determined by the lowestpitch in therange of the singer. The next higher octave isnawa and the secondtuti.[1] However, from these twenty-four tones, seven are selected to produce ascale and thus the interval of a quarter tone is never used and the three-quarter tone orneutral second should be considered the characteristic interval.[2]
By contrast, in the Europeanequally tempered scale, the octave is divided into twelve equal divisions, or exactly half as many as the Arab system. Thus, when Arabic music is written in Europeanmusical notation, a slashed or reversed flat sign is used to indicate a quarter-tone flat, a standard flat symbol for a half-toneflat, and a flat sign combined with a slashed or reversed flat sign for a three-quarter-tone flat, sharp with one vertical line for quarter sharps, standard sharp symbol (♯) for a half-stepsharp, and a sharp with three vertical lines for a three-quarter-tone sharp. A two octave range starting withyakah arbitrarily on the G below middle C is used.[3]
In practice, much fewer than twenty-four tones are used in a single performance. All twenty-four tones are individual pitches differentiated into ahierarchy of important pitches—pillars—which occur more frequently in thetone rows of traditional music and most often begin tone rows, and scattered less important or rarely occurring pitches (seetonality).[4]
The specific notes used in a piece will be part of one of more than seventymodes ormaqam rows named after characteristic tones that are rarely the first tone (unlike in European-influenced music theory where thetonic is listed first). The rows areheptatonic and constructed fromaugmented,major,neutral, andminor seconds. Many different but similar ratios are proposed for the frequency ratios of the tones of each row and performance practice, as of 1996, has not been investigated using electronic measurements.[5]
The current tone system is derived from the work ofFarabi (d. 950 CE) (heptatonic scales constructed from seconds), who used a 25-tone unequal scale (seetetrachord), andMikha'il Mishaqah (1800–1888) who first presented the 24-tone equal-tempered division.[6] Some strict traditionalists and musicians also use a17-tone set, rejecting the 24-tone division as commercial.[7]