Yay free mood music for all. Not all of it fits 40k but a simple listen thru and arrangement of the songs into playlists based on mood and you have a veritable gaming library of soundtracks to play with your every game. One of the better groups that you should start with to get a nice smattering of score music to form your playlist is Epic Score. You will find a ton of the albums from this group free with Amazon's Prime Music. Just grab them and put them on shuffle play for your first outing. Very few of the songs are not really 40k appropriate, and you can trim them from your playlist as you hit them.