I've been an avid listener of cinematic/epic genre tracks for some time now, I personally find it to be my favourite category of music for anything focus related. If you aren't doing anything but relaxing, it is the type of music that gets your imagination going once you have been immersed. The combinations of euphonious sounds can sometimes even give you goosebumps. We're talking about the same style of music that is nearly always chosen to score Hollywood action movies. It works because it gets people listening engaged, and adds another medium to the visuals on-screen. I have recently created a playlist containing the most moving, soul-touching epic genre soundtracks that I have listened to over the past several years. It is the stuff that really spurs you on if you are doing any task, or lets your mind roam free if you are simply relaxing.
I call this collection "Epic Music to take you on an Aventure". Immerse yourself, and let your imagination come to life.