Complex sentence: At that time, the reigning superstar of Carnatic music was none other than G. N. Balasubramaniam or better known as GNB & indeed, Kalyanaraman sang in the GNB bani even before becoming the disciple of his idol.
Split into simpler sentences: At that time, the reigning superstar of Carnatic music was none other than G. N. Balasubramaniam or better known as GNB. Indeed, Kalyanaraman sang in the GNB bani even before becoming the disciple of his idol.