Came across this video of Bear McCreary explaining the opening title theme. He talks about how the title music changes and evolves with every episode. Pretty cool stuff. Then there is more insight into other parts of the scores used early on in the series, and lots more content throughout his site.
http://www.bearmccreary.com/#blog/th...days-gone-bye/
EDIT:
E.g. here's him talking about the score in the latest episode: