First: if you have not seen the paly 'War Horse', stop reading and go out to buy your ticket now. Believe the hype. The production will blow you away. Admittedly I was a little reluctant to go see it myself, I'm not a big 'Black Beauty' fan, but I must say this show is just amazing. The movie version is such a different experience you should really regard them as only slightly related. And that brings us to the score, which the film doesn't use, replacing it by an equally brilliant John Williams soundtrack.
The music is very fitting for what you get to see on stage and you'll never hear a more heartwrenching rendition of 'the year turns 'round again'.