If you do get an answer, i'd like to know too. It seems running two apps at the same time is beyond it. Ok I understand games need sound too, but I would like too listen to music whele surfing or reading ebooks.
To play music in the background, you need to customize the setting of the current running application. Choose the music that you wish play in the background.
check the setting first if you have marked the "background playing" button... then try to play a song... instead of pressing the back button, try home button.... well, this could be the simplest answer.... if is still not working... ahhhmmmm guess you need to standby for more techy answers...