Appearing and Falling objects in music game

Hi guys, I have a question regarding the music games. Example on many games out there have the falling objects and the music playing on the background as the game started. How did they manage to do the objects start falling as the music start playing and it is not falling anymore as the music stopped, and of course the falling objects is not fall randomize instead the falling objects will fall as the certain note (note for sound) playing. Thanks. This is the example game: http://www.kongregate.com/games/reflexive/music-catch-2