Would it be possible to re-compose the same orchestral music from the
soundtrack that has vocal singing in it?

Simplest-ga, didn't you like my comment to your identical previous question?
It still stands, with this additional comment to your clarification:
All of us learn the melodies of songs by listening to them, and when
memorized, a half-way musically literate person can pick out the tune
on a piano and write it down.  A professional musician will probably
be able to recognize chords played on a piano and write them at once 
- two, three or four notes.  I cannot, but I do know musicians who can
immediately name a chord that they hear.

Hi myoarin, sorry about that. It is not that I dislike your comment. IS that 
I make the question looks like multiple questions type :P... Sorry about that.

no problem, I had my answer about singing drafted but could not post it.
I bet with electronic filters computers can also do this quite well,
perhaps need a little human correction afterwards,
someone may know about this ...