The last few seconds of ending in 'Sahana' was completely Rahman anna's idea.. It took me a few takes to get in to the raga 'Sahana' and out of the song 'Sahana'.
I got several plaudits for this one too and there were people telling me that the end is one of the best portions in the song, and also asked me on how that short bit came into being.
Like ever, I guess Rahman anna conjured it out from where, God knows. He said, end it in Sahana, he sang the bit and all that I had to do is repeat :)