Sundaram sings the mantra Nataraja Nataraja on a Saturday evening satsang:
Natarājā Natarājā Shiva Shiva Shambo
Natarājā Natarājā Mahādeva Shambo
Om Namah Shivaya ....
... Natarājā Natarājā.
Unfortunately, you can not find this version of Nataraja in the Yoga Vidya Kirtan songbook. Under the number 254 you will find a different one. Nataraja is a powerful and moving mantra praising Shiva, "the Dancing God" - and one of his many names is "Nataraja". - A recording of Yoga Vidya Bad Meinberg, Germany.