Crescendo Events are actions that cause a massive onslaught of Common Infected, often called a Horde, to find and attack the Survivors. The cause is often a part of the environment that the Survivors must activate in order to progress through a level, generally acting as mini-finales. An important factor during game play is that Special Infected (including Tanks) are invariably intermingled or interspersed with Common Infected during Crescendo Events. Most Crescendo Events involve causing a loud noise or bright object to appear, which attracts the Infected.