What is the fine-grained topic of the following text: From his adolescence, Ranajit, a child prodigy initially with mandoline but later after rigourous training and practising in sarod under his teachers Late Ustad Dhyanesh Khan and Ustad Ashish Khan of Maihar Gharana, established himself as one of the best musician of his generation. Only return the topic.
Ranajit's musical journey and accomplishments in sarod.