Numerical digit
From India, the thriving trade between Islamic sultans and Africa carried the concept to Cairo. Arabic mathematicians extended the system to include decimal fractions, and Muḥammad ibn Mūsā al-Ḵwārizmī wrote an important work about it in the 9th  century. The modern Arabic numerals were introduced to Europe with the translation of this work in the 12th century in Spain and Leonardo of Pisa's "Liber Abaci" of 1201. In Europe, the complete Indian system with the zero was derived from the Arabs in the 12th century.
Arabic maqam
Since microtonal intervals are impractical to accurately notate, a simplified musical notation system was adopted in Arabic music at the turn of the 20th century. Starting with a chromatic scale, the Arabic scale is divided into 24 equal quarter tones, where a quarter tone equals half a semitone in a 12 tone equal-tempered scale. In this notation system all notes in a "maqam" scale are rounded to the nearest quarter tone.