Which prominent musicologist was responsible for categorizing Hindustani classical music into ten fundamental parental scales, known as the Thaat framework?

The correct answer is Pandit Vishnu Narayan Bhatkhande.

Pandit Vishnu Narayan Bhatkhande (1860–1936) was an eminent Indian musicologist who carried out a comprehensive structural analysis of Hindustani classical music. One of his most significant contributions was the re-organization and classification of Hindustani raga systems into ten primary scale structures, known as Thaats.

The ten fundamental Thaats introduced in his system are:
1. Bilawal
2. Kalyan
3. Khamaj
4. Kafi
5. Asavari
6. Bhairav
7. Bhairavi
8. Todi
9. Poorvi
10. Marwa

This framework greatly simplified the study, performance, and documentation of Indian classical music, making Pandit Vishnu Narayan Bhatkhande a pioneering figure in modern musicology.