The game's simple background music, a four-note ostinato which repeats continuously throughout gameplay, increases in tempo as time goes on and the aliens descend upon the player.
[citation needed] In Dead Space 2, the background music appears to be arranged into four layers, each a stereo track corresponding with a specific level of "fear".
Each of these layers is then either individually or collectively mixed during gameplay depending on a variety of game variables, such as the distance the player is from enemies.
[citation needed] Spore uses an embedded version of the music software Pure Data to generate music according to certain game events such as the phase of gameplay, the player's actions in the "creature editor", and the duration of the gameplay session.
[8] In addition, Ape Out features a procedurally generated jazz soundtrack which changes based on the intensity of gameplay and the players inputs.
[9] Some video games, such as Rez and Extase, synchronise their sound effects with the background music to blend them together.