 The opening theme of the game features a neo @-@ Gregorian chant , which was performed in studio by a 135 @-@ voice choir . Much of the underscore music that plays when the player is exploring the game , rather than during cinematic scenes , is based upon that opening scene . The composers made use of silence in many scenes , to build up tension for moments of a " pounce " effect , creating the effect with music that something is catching the listener . They deliberately saved the most intense music for the final chapter of Phantasmagoria , when the game becomes the most intense . During some chase scenes , drums and low strings are used in the score to simulate a heartbeat , which grows louder and louder during more dangerous moments . 
