Idk maybe I'm odd but I don't listen to music when I game. I keep the d2 sound on around 30% so its still audible but not overwhelming and generally run a season of tv shows on a different device as background noise.
I've also dabbled into studies of neurology and psych though and feel while the music does add extra stimulation to the event can lead to the listener becoming more energized, more manic-impulsive, and more likely to make poor decisions which can greatly impair ones ability especially on something like hardcore in comparison to something more mellow-relaxing that achieves higher focus. Its about body rhythms if the rhythm helps you get into it and achieve better results go for it, if you are noticing slips maybe alter your environment to be less distracting, lower energy, etc..
Not telling anyone how to play, in the end if you're having fun that is all that matters.