Some info from the Julian D. A. Wiseman site:
The links below ring a (vague) bell so if I (or anyone else) have posted this previously apologies in advance:
http://www.jdawiseman.com/papers/games/jsw2/jsw2_programmer_comments.html (http://www.jdawiseman.com/papers/games/jsw2/jsw2_programmer_comments.html)
http://www.jdawiseman.com/papers/games/jsw2/jsw2_index.html (http://www.jdawiseman.com/papers/games/jsw2/jsw2_index.html)
https://stevewetherill.com/2013/08/25/jet-set-willy-the-final-frontier-the-music/ (https://stevewetherill.com/2013/08/25/jet-set-willy-the-final-frontier-the-music/)
http://www.jdawiseman.com/papers/games/jsw2/jsw2_updated.html (http://www.jdawiseman.com/papers/games/jsw2/jsw2_updated.html)