A.R.Rahman in Apple Interview says
Describe your method for scoring a film.
I mostly don't write to specifically defined cues. I just watch the film a couple of times, stop watching it, then write something that comes to my mind from the film. This way, when I try to sync the music, the results are that much more wholesome. You get something extra that you don't get when you're looking at specific points in the timeline. The music is much more organic this way, not jumping cue to cue. It's more about counterpointing and, sometimes, walking hand-in-hand. Most of the time it works out. If you watch the picture and try to have a specific chord change here, a tempo change there, when the director comes back and wants to move picture, you find that you've wasted time. I think this way is more appealing to me and to the people watching the film. Click tracks and following the SMPTE are necessary for some things, but once you have everything in Logic, then afterwards you can edit and make minor changes.
Rahman’s is a complete antithesis to way Illayaraja works and yet his music works equally well (at least for me) – This bewildering thought never stops to amaze me.