There are so many variables that may have something to do with that.
What is your computer OS? What program are you using to play back the music? What type of music files are you trying to listen to? Does that problem occur with only one type of music file or all of them? Does the problem occur if you try listening to a music CD? What type of sound card do you have? Does the program you are using have a graphic equalizer or other advanced settings? Have you tried using a different program for playback?