Latent Dirichlet Allocation Model for Raga Identification of Carnatic Music

摘要

Problem statement: In this study the Raga of South Indian Carnatic music is determined by constructing a model. Raga is a pre-determined arrangement of notes, which is characterized by an Arohana and Avarohana, which is the ascending and descending arrangement of notes and Raga lakshana. Approach: In this study a Latent Dirichlet Allocation (LDA) model was constructed to identify the Raga of South Indian Carnatic music. LDA was an unsupervised statistical approach which was being used for document classification to determine the underlying topics in a given document. The construction of LDA was based on the assumption that notes of a given music piece could be mapped to the words in a topic and topics in a document could be mapped to the Raga. The identification of notes was very difficult due to the narrow range of frequency and the characteristics of Carnatic music. This inclined us in moving to a probabilistic approach for the identification of Raga. In this study we identify the notes of a given signal and using these notes and Raga lakshana, a probabilistic model in terms of LDA's parameters ∝ and θ were computed and constructed for every Raga by initially assuming a value which was constant for every Raga. This value of ∝ was cultured after determining θ for a given Raga. The θ of a given Raga was computed using the characteristic phrases which was a sequence of notes and was unique for a given Raga. During the Raga identification phase, the value of ∝ and θ were computed and was matched with the constructed LDA model to identify the given Raga. Results: Using this model, the Raga identification of Parent Ragas had a lower error rate than that of Child Raga. For parent Raga an average identification rate of 75% was achieved. Conclusion/Recommendations: The accuracy of the algorithm can be improved by using more features of Raga lakshana. After identifying the Raga, it can be used as features to be used by a Music Information Retrieval system.