I'm just blown away by this song for its ease, spontaneity, conceptual brilliance, and "feel goodness". To even think of composing such a song in swing/jazz mode showcase Rahman's tremendous innovativeness and originality and out of the box creative thinking. Notice how ARR has sung it so effortlessly in that octave range. His smooth voice is so suited for this type of music....almost reminds me of Mel Tourmet...another great singer of the past who used to sing such type of jazzy songs. The swing rhythms are so catchy. I just love the trumpet improvisation that keeps weaving in and out throughout the song, similarly how the accordian weaves in and out in Ay Hairathe and Ishq Ada. It's a Rahman specialty to have one single acoustic instrument weave into songs like that and take center stage. And the soft chords in the background with piano touches and female voice bursts just adds icing on the cake.
I hope more of us and more people in general will appreciate how truly special this song is.