With the coming of Islam to Iran there occurred a most important confluence of two musics, Arabian and Persian. A closeness between them persisted for at least two centuries,especially during the Golden Age of the Abbasid caliphate at Baghdad. At this time there was such a blending of musical styles, instruments, and terminology that the question of which music most influenced the other is still hotly debated thirteen centuries later. Historians of Persian art are fond of the doctrine that the Arabs, coming straight from the desert to a more advanced civilization in Persia, adopted the art and music of the vanquished culture. Moreover, Persian musicians claim that Persian music must have strongly influenced Arabian music because Persian musicians were favored in the Arab royal courts, Persian instruments were introduced, and a great deal of Persian musical terminology came into Arabic music. Arab musicians, on the other hand, feel that their music was the basis for Persian music because there are equally as many Arabic words used in Persian music terminology. The Islamic period produced more writings on music than any other. As a sampling, Farmer lists twenty-eight music theorists from the eighth to the twelfth centuries, claiming that these are only the "most important" and that the list excludes littérateurs and biographers. But there are also numerous writings in the latter category. The monumental Kitab al Aghani by Abul Faraj al-Isfahani (897-967), now in a twenty-one volume edition, lists the virtuosi of the period and the music they played—a sort of Grove's dictionary of the day ! Finally, apart from theoretical and historical writings, there are many vehement religious discussions concerning the illegality of music in Islam and equally many tracts written in defense of music.From records of musical activity in the royal courts, it appears that some caliphs, while awaiting the outcome of the theological disputes, actively championed music. A few of these rulers were musicians themselves, and during their reigns, royal patronage of music was considerable. Among the musicians in the court of the Abbasid caliphs, two of the most celebrated were of Persian descent: Ibrahim al-Mausili (d. 804), who was patronized by Harun al-Rashid, and his son Ishaq al-Mausili (767-850). (Source: Persian Classic Music).