Yes, Sam is right. Sri R.S. Gopalakrishnan, who was based in Mylapore, was also the guru of Nagai Muralidharan.
He also accompanied Smt MSS quite extensively and I think he might have recorded the world famous Venkatesa suprabhatam LP with her. Perhaps Cienu can add to this?
Sri R.S.Gopalakrishnan accompanied Smt MSS on her 1963 tour to Edinburgh and Cairo. The other accompanying artists on the trip were Sri T.K.Murthy and Sri Alangudi Ramachandran. And Ramesh is absolutely right on the Venkatesa Suprabatham LP which was recorded just before the 1963 trip.
Please find below a picture of the artists. From the Jamakalam , this looks like a wedding concert at Hotel Ashoka, Chennai. (Smt Vijaya Rajendran is playing the Tambura and providing vocal accompaniment)