This youtube entry is that of the song Navarathiri Koothu http://www.youtube.com/watch?v=PTV77pK_z38 from the movie Navarathiri. Inspite of the song being based on the old koothu format, I guess the music is heavily influenced by nuanced carnatic music.
I wonder who are the background singers for this item. My guesses are TMS & P Susheela. Who else? Who is the singer for the 0:30 to 0:44 seconds of the song. It is so fantastic. There are also other such fantastic moments especially between 5:00 and 5:40 of the song.
A fantastic experience to listen to it. For your pleasure!