Introduction:
Swaramela Kala Nidhi is a treatise on music that was written by Ramamatya. This text holds great significance in the field of Indian classical music and provides valuable insights into the musical concepts and traditions of the time. Ramamatya was a notable musicologist and composer who lived during the 16th century.

Explanation:
1. Authorship:
The correct answer to the question is option 'D' - Ramamatya. Ramamatya was a prominent scholar and musician from South India who is known for his contributions to the field of musicology. He is believed to have composed the Swaramela Kala Nidhi, which is considered to be one of his most significant works.

2. Content and Significance:
Swaramela Kala Nidhi is a comprehensive treatise on music that covers various aspects of Indian classical music. It provides detailed explanations of ragas, melodic structures, rhythmic patterns, and other foundational elements of music. The text also includes guidance on vocal techniques, improvisation, and composition.

Ramamatya's work is highly regarded for its systematic approach to music theory and its emphasis on the importance of practice and discipline in musical training. Swaramela Kala Nidhi is considered a valuable resource for both musicians and scholars interested in understanding the intricacies of Indian classical music.

3. Influence and Legacy:
Ramamatya's Swaramela Kala Nidhi has had a lasting impact on the development of Indian classical music. His work provided a foundation for subsequent musicologists and composers to build upon. It contributed to the evolution and refinement of music theory and helped shape the pedagogical methods used in music education.

The concepts and principles outlined in Swaramela Kala Nidhi continue to be studied and practiced by musicians and scholars today. Ramamatya's work played a significant role in preserving and transmitting the rich musical heritage of India, making it an important contribution to the cultural legacy of the country.

Conclusion:
In conclusion, Swaramela Kala Nidhi was written by Ramamatya, a renowned musicologist and composer. His treatise on music has had a profound influence on Indian classical music and continues to be a valuable resource for musicians and scholars. The work showcases Ramamatya's deep understanding of music theory and his dedication to preserving and promoting the art form.