There is a video on youtube called Halo | Ultimate Theme Mashup and I really think that the guy who made that video did something fantastic. He combines the best music from all games into one soundtrack. Now in my opinion, Halo 4 and Halo 5 music was mediocre and thats because the music for halo games has been set to such a high standard so it's really hard to recreate what Marty O' Donnell did. Now I say instead of trying to do new music just use old music from old games along with new music. Halo 4 didn't play the main halo theme once I believe and that's insane. Once again I mention this video this guy did because it is such a great mashup of all the great halo music.