Adding Music to a Level

On each of the levels I have added background music which is appropriate for each level. To add music to the level I created a new layer on the main timeline and named it 'sound'. Then I went to File>Import>Import to Library and select the music that I wanted to add. Once it was in my library, I made sure I was on the sound layer and then dragged the sound from the library and dropped it onto the stage. When the user enters a level the music starts automatically and is stopped when the user exits a certain level.