Music plays on your emotions. I would assume that since emotions can change how you fight music can too (indirectly).
Try doing a serious bag workout to The Blue Danube and then to Rage Against The Machine. Which do you think works better?
I think music can directly AND indirectly influence your practice, but in an actual fight it'd probably be good to have your mind focussing on the fight, and not on some song. Jack
On a somewhat unrelated note, I find it a great way to develop broken rhythm by actually "playing" my heavy bag to a percussion part. What a great way to confuse people, playing them with your fists like theyre some kind of drum! But anyways, you bet music can affect your performance. But as with any emotion getting too much of a hold of you, theres good and bad to it. I'm willing to wager that if youre in a fight and all thats going through you head is seek & destroy by metallica, youre probably not going to be thinking about any possible counter attacks or retaliation, just hurting the guy. Thats a fairly dangerous mindset, if you ask me. Dont get me wrong though, it has its place. Some good metal can really rejuvenate you after youve been doing pad work for a half hour, and then the villainous sifu proclaims its thai pad 4-count time. Likewise, if youre working on something like a trapping exercise, perhaps its not the best idea to have killing and maiming music going. But in a real fight, trying to encourage the flames of any emotion too much will cause how youre fighting to take a swing toward it, and as such, its probably not the best idea. One could argue that you could recall different songs appropriate to how the fight is going, but if you ask me, if you devote too much mental effort to something not directly involved in where you are and what youre doing, youre probably going to get punched in the face when youre "selecting tracks" so to speak.
Music does influence the fighter, think of Thai and the "cat strangling" music they fight to. Thats why they go around elbowing each other in the head in a vain attempt to drown out the music. If there wasnt that tune the fights wouldnt be half as violent.
