Why the snarky answers???
I am asking where this comes from. As in, I want to know what I am buying. Is this done by ear with a good deal of guesswork, or...?
Sorry not meant to come across as snarky (and I actually thought I was being quite witty. I guess that's British humour/humor for you). We thought you meant "where are they shipping from?", since one of the challenges with buying these can be the significant international shipping fees.
What you meant was "how was this created?", quite a different question. The answer is, I had high resolution scans of James's score sheets, plus my ears to check for podium changes using the Varese Sarabande soundtrack album, to which this book acts as a companion piece.