Dear Suresh Ji
Yes indeed a wonderful analysis. Your last line -
It is not the Synth. It could be the Sound recording. It definitely is the Melody. Melody is all!
- Really gets to the core and definitely sums your write-up.
BTW SEL also used that loop for Lakshya title song and though I'm not sure I think GVP has used that same effect if not loop for Pirai Thedum and the later is one of my most fav songs of 2011. So yes, this further supports the argument of melody being the biggest lifeline of a song/instrumental. The melody has to be concrete from whoever composes it, but to an extent that too depends on the listeners taste.
The last tracks from Raaja Saab with complete emotional synth overdose are Neeral Udal Kazhuvi (Sounds like a cousin of Celebration of life from Aayrathil Oruvan) and Thedi Vantha (Ponnar Shankar). These two tracks, have tall pillars in all three categories i.e. Synth, Sound-engineering and melody.
Digression//
To those, who think Synth arrangements make the refreshing quotient less compared live recording - I just have to say one word "VANGELIS".