Hmm . . . this may explain why I've been running pretty well without music, ever since my second set of headphones crapped out a few months ago:
[A]ccording to [Dr. Costas] Karageorghis, the benefits of listening to music decrease with the level of intensity of the running. The faster you run, he explains, the less effect the music has.
"Elite athletes," says Karageorghis, "are usually 'associators', which means they tend to focus inwardly when they are running." Most other runners, he says, are "dissociators" (or are somewhere between the two). This means they look for stimulus and distraction from what is going on around them. "Judging by your times," he says, "you are probably an associator."
I'm not in the same class as the author, but when it comes to my hard/hardish workouts (intervals and tempo runs), I don't really look for distraction. That's especially true for the interval runs.
On the other hand, on my long slow distance runs, I do manage to get quite a bit of reading done on my Kindle Fire, if I'm running on the treadmill. But that's because the treadmill gets boring when you're on it for 80+ minutes.