If you are a Horner's fan must take a look at https://www.ditart.com/horner.
I love Horner's scores specially A Beautiful Mind and Braveheart.
There is another website. https://www.backtotitanic.com/makingof.html
As the it shows this site have a lot of cool stuffs about Titanic's soundtrack.
If you know any other site please type it here.