You could transfer the music to your sd card and then use something like root explorer to copy the files to the internal memory, but as others have stated, it's not really the right place for music. The one exception would be if your trying to add ring tones and notification sounds. I do this Nd copy my files directly to system/media just so they stay even if the ad card isn't accessible. But if it's just music you want to listen to, you're better off keeping it on the sd card.