<P> The modern Arab tone system, or system of musical tuning, is based upon the theoretical division of the octave into twenty - four equal divisions or 24 - tone equal temperament (24 - TET), the distance between each successive note being a quarter tone (50 cents). Each tone has its own name not repeated in different octaves, unlike systems featuring octave equivalency . The lowest tone is named yakah and is determined by the lowest pitch in the range of the singer . The next higher octave is nawa and the second tuti . However, from these twenty - four tones, seven are selected to produce a scale and thus the interval of a quarter tone is never used and the three - quarter tone or neutral second should be considered the characteristic interval . </P> <P> By contrast, in the European equally tempered scale the octave is divided into twelve equal divisions, or exactly half as many as the Arab system . Thus the system is written in European musical notation using a slashed flat for quarter flat (some systems use a reversed flat sign instead), a flat for half - tone flat, a slashed flat and a flat for three - quarter tone flat, sharp with one vertical line for quarter sharp, sharp (♯) for half - step sharp, and a half sharp and a sharp for three - quarter sharp . A two octave range starting with yakah arbitrarily on the G below middle C is used . </P>

The arabic modal system divides the octave into how many notes
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