 While he was making "Illalu", the playback system became popular.Among the classical ragas, Rao liked "Bhimplas (Abheri)", "Sindhu Bhairavi", "Kafi", "Kalyani", "Pahad" and "Malkauns (Hindolam)", which he used most frequently in his songs.His two assistants (for over four decades), Rajagopal and Krishnan – both well-versed in classical music – were an asset to him.