However, no Infected has a 'Bacteria' with only one note, seven notes or nine notes. A theme played on piano means that a Special Infected has spawned nearby, while a theme played on strings (violin, viola, cello, or double bass) indicates that a Special Infected has spawned further away, or in the distance.
Every Special Infected's 'Bacteria' have their own select number of notes, and two versions of said notes played on piano and string. They also have a song that plays when their attacks hit. They each have their own tune to identify them by. ' Bacteria' is a name for the Special Infected jingle that plays when one is around. This usage of an often-repeated cue in Left 4 Dead 's soundtrack is similar to how some real-life movies have cues (or leitmotifs) which recur throughout their soundtracks. The noticeable cue in this song reoccurs in many other musical pieces in the game, such as in the Tank's themes.
' Left 4 Dead' is the main theme of the game.
