Why are Muslim musicians so prominent both as singers and as instrumentalists at all levels of Indian music, classical, semi-classical, folk, pop, ghazal and so on?
It is absolutely correct that Indian music in all forms including the main Raagas and Raaginis originated long before the arrival of Islam and Muslims in the subcontinent. The general understanding is that all forms of music Hindustani as well as Carnatic, originated in the folk songs and melodies which were then refined and sublimated as ragas and raginis.
Hindu rituals in the temples were performed to the accompaniment of dance and music purported to please the gods and goddesses. Therefore, during the 'Hindu period', music remained essentially devotional although it was patronized for entertainment as well by rulers and princes.
The arrival of Islam and Muslims brought along a puritanical way of life, with a lot of do’s and dont’s. Once settled in India, they became a part of the overall Indian culture and music inevitably became part of the sensibilities and aesthetics of the Muslims which included both those of foreign origin as well as the local converts.
Obviously the Arabs as well as Turco-Afghans too had music in their cultural baggage, notwithstanding the restrictions of puritanical Islam.
Amir Khusrau is reputed to have devised Raag Yaman/Aimen. Several other ragas were devised by Muslim musicians but all this happened in the pluralist culture which is typically Indian.
Over the centuries, Islam and Muslims became indigenized with the amalgamation of culture and religion. This is how the rest of the world also sees us in spite of our habit of naming ancestors from outside India.
During the high period of Muslim rule, from the time of the Sultanate to the Mughals, the emperors, princes and nawabs began to patronize music which more than devotion became a stimulant of sensuality and entertainment.
The royal courts were closed to the general public and that meant the Muslim clergy was also kept away when the ruler wanted entertainment. As a result, many people began to play music for the court. That naturally meant conversion of local musicians to Islam.
Another route for Muslim involvement in music was the Mehfil-e-Samaa which some Sufi orders began to incorporate into their congregations. Sufis played music and began to dance in moments of pure ecstasy and rapture as part of their meditative practices.
Puritanical Islam was eclipsed by popular Islam which was a synthesis of subcontinent, Islam and syncretic movements such as the Gorakhnathis, Bhaktis and so on.
The Sikh gurus patronized music and some Muslim musicians, since the beginning, were a part of the Sikh prayers and worship practices.
Muslim musicians had a head start over all others because they were available not just for devotional music as many Hindus were, but also for princes and nawabs and in the Red Light Areas or heera mandis.
With the decline of Mughal rule and the British emerging as the dominant power, Muslim musicians who had been receiving patronage for a long time now sought employment with all rulers including those in the Punjab, where several Sikh princes were in power.
With the advent of radio and films, a new genre of music emerged: the three minute long songs.
During the era of silent films, every cinema house had live orchestra playing music in the background. The era of the ‘talkies’ provided further employment chances to musicians as the music director became the key composer. No idea of a music director existed before the era of radio and films.
The rise of puritanical Islam meant that many musicians converted to Shia-ism, where marsia and other forms of devotion gave greater scope to music while others became qawwals and remained followers of sufi Islam.
I hope this explains why there is a very large number of Muslim maestros in the field of music because the Muslims of the Indian Subcontinent are of a very rich lineage of arts, no matter how much we emphasize on the Middle Eastern and Central Asian origins of Islam.