R. Lakshminarayanan, R. Vaidhyanathan, Latha Venkataraman and Kalyani Viswanathan have been on the most prominent of Carnatic concert stages for 15-50 years. Yet, most readers would not know who they are. They are tambura players – unknown, unnoticed and mostly uncredited. Vocalist Nisha Rajagopalan cannot imagine performing on stage without…