Quoting from Wikipedia:
Pareidolia (/ˌpær.iˈdoʊ.li.ə, ˌpɛr-/; also US: /ˌpɛr.aɪˈdoʊ.li.ə, -ˈdoʊl.jə/) is the tendency for perception to impose a meaningful interpretation on a nebulous stimulus, usually visual, so that one sees an object, pattern, or meaning where there is none.
Common examples are perceived images of animals, faces, or objects in cloud formations, seeing faces in inanimate objects, or lunar pareidolia like the Man in the Moon or the Moon rabbit. The concept of pareidolia may extend to include hidden messages in recorded music played in reverse or at higher- or lower-than-normal speeds, and hearing voices (mainly indistinct) or music in random noise, such as that produced by air conditioners or fans.
Scientists have taught computers to use visual clues to “see” faces and other images.From Wikipedia
In other words, according to Wikipedia, a pareidolia is an illusion, pareidolias do not exist. Yet we all know in many cultures an ancient tradition exists of watching clouds in the sky to spot recognizable patterns resembling an intelligible shape or image. This is clearly suggested in one of the finest ancient Greek comedies, “The Clouds” by Aristophanes, which premiered in the IV Century BC.
But did you know written text and sound files can produce pareidolias?
I wrote a few programs to convert text and sound files to images. You can download them from this website. Have fun watching hidden images in your favorite music or other sound recordings, poems, novels, articles or song lyrics.