Yes, there are actually quite a few tracks within Halo 5 that are not included in the Halo 5: Guardians OST album. A lot of these tracks are exclusive to Arena gamemodes, and I’ve cataloged most of them into this video:
https://www.youtube.com/watch?v=yO6mu2wD1eY
I’m still working on getting the remainders, but I hope you all enjoy what I’ve gathered so far!