Ao Oni uses a large number of free and stock RPG sound effects and music. The frightening music and ambient breathing heard during the game have become staples of the genre and are signature themes.
Horor-b.mid (horor-b.wav in Version 6.23) is an instrumental track that plays during the chase scenes with the oni . The minimalistic track is jarring and dissonant, and is felt by many players to be uncomfortable or even disturbing. The track has become the signature theme of the game and the oni itself. Most of the fanmade spinoff games also use this theme.
In efficient game design, the midi engine should be started as the game boots up, but in previous versions of the game it is launched as soon as the music should be playing. On some older computers, this takes a few seconds, resulting in a few seconds of lag and game-freezing every time the oni is set to appear during random encounters.
A5_16491.wav is a haunting instrumental track that usually plays during the first encounter with the oni. In all versions of the game and fanmade spinoffs, this ambient music plays when the player is about the witness the oni for the first time. The music is ambient and dissonant, and be described as "creepy."
The Oni's SoundsEdit
The oni itself makes a number of sounds. In Version 3.0 , a low whispering sound is made during a scene where the final oni appears. The whispering sound, titled A5_12362.WAV, consists of 19 seconds of incoherent mumbling in what could be a child's voice.
The oni also is associated with a heavy breathing sound that plays during certain scenes or locations. During chase scenes where the player hides in the closet, the breathing sound is played when the oni enters the room. In later versions, the breathing sound is looped continuously when the player enters the annex basement . The breathing sound origin comes from one of the default RPG Maker XP Files. It is known as 017-Creatue01.wav.
In Version 1.0 a loud, startling sound called bikkuri.wav (bikkuri びっくり means "surprised") is played when the player discovers a corpse in the bathtub. Although this sound is unused in later versions, it can still be found in the sound effect folder. A large drum is struck and a shrill violin draw is played for two seconds. The sound is used in certain fanmade games like Siro Oni or Hakkyo Oni as an announcement of the oni's arrival.
A random fact is that bikkuri.wav is actually taken form the visual novel, Higurashi no Naku Koro ni, a game that Ao Oni probably used for inspiration as they have a lot in common.
In all versions of Ao Oni there are unused Audio files. These may simply be carried over files from previous versions, but in version 1.0, 2 audio files exist that are not present in any version. One of these files, saiv.mid, sounds like a piano played speedily with a high pitched instrument accompanying it. The other, BGM008.ogg, is what sounds like high notes on a piano with short periods of silence containing sharp notes. This track, much like A5_16491, can be described as "creepy."