To concentrate and focus, I simply tell myself to do it and make it happen. Nothing is more valuable than believing you can do something and then trying your best to achieve it. (Skip the excuses and time wasters.) I don't care who is an introvert and who is an extravert, we all have amazing minds that are quite capable of doing many things.
As far as music goes, well, I just love listening to music all the time anyway. If I'm weight lifting or cleaning, I might listen to louder, heavier, and faster music, and if I'm painting or writing, I might listen to quiter and slower music. I don't know if I use it to help me in the second case, I just love listening to music.
I think what really happens is that music helps you WANT to focus. For some people, intensely focused thought in extreme silence is freaky, and the music probably just helps them feel more at ease. It takes a litte bit of the pressure off of them because there's something else in their awareness that's continuous and requires no mental energy. It helps you keep track of time and feel relaxed. Maybe it even helps you from overloading by cutting your focus down to a more effective level. (You can't win a marathon by running full speed.) That's just my theory, anyway.