Short answers, pulled from the story.
Hindustani classical music split from its southern counterpart in the 12th century. This divergence occurred when northern regions of the Indian subcontinent began developing distinct melodic and rhythmic systems.
Amir Khusro lived from 1253 to 1325 and became a pivotal figure during the era of Islamic rule under the Delhi Sultanate. He systematized aspects of Hindustani music, introduced ragas such as Yaman Kalyan, Zeelaf, and Sarpada, and created six genres including khyal, tarana, Naqsh, Gul, Qaul, and Qalbana.
Until the late 19th century, instruction happened on a one-on-one basis within the guru-shishya system where a guru passed knowledge to a shishya or student. Many students spent most of their time serving their guru in hopes of receiving a single piece or nuance known as a cheez.
Vishnu Digambar Paluskar founded the Gandharva Mahavidyalaya school in Lahore in 1901 while Vishnu Narayan Bhatkhande conducted research visits between 1909 and 1932 to collect compositions from numerous gharanas. These efforts fostered a movement away from the closed gharana system through public support, donations, and standardized grading systems.
Ancient treatises like the Natya Shastra by Bharata from the 2nd and 3rd century CE and Dattilam from probably the 3rd and 4th century CE refined these principles. Sharangadeva composed the Sangita Ratnakara in the 13th century which includes names like Turushka Todi revealing an influx of ideas from Islamic culture.