Fearful Harmony is the name given to the startup error on the PlayStation 1 whenever the user inserts a non-PSX disc or a busted or pirated PS1 game.
On startup, the Sony Logo will appear as normal and then in most cases, it will attempt to boot up the improper disc in the PS1, however, it will play the second sound without the PlayStation logo. This sound is different to the normal PS1 bootup sound. The word 'Sony' will still be on the screen, and the orange-yellow diamond will still be there too.
After about a minute or less, a chime will play for a while, which was known to terrify children and would be unpleasant to adults.
This error screen varies, depending on what disc you've inserted and what PS1 model you have. Some show the diamond, the acronym SCEA, and the word PlayStation will be appearing and disappearing.
Both the sound and the graphics appear to "frame-advance", the startup screen is progressively continuing in a very slow pace, possibly the result of the system trying to read and interpret the invalid data off the disc, which would have finished by this time with a normal game, but since it's still trying to find the proper data, the loading screen is "lagging", slow enough that the chimes are slowly coming in. The Fearful Harmony ends once the system gives up, or finishes scanning for the data it was looking for.
PSX Personified Fear
This, though less frightening, happens for the same reason with unreadable PSX games. The startup screen will show, followed by a black screen with a horrible sound. After the sound, the screen will stay dark, making users expect a jumpscare.
The "horrible sound" mentioned above is glass shattering pitched down and reversed. This sound is played when normally transitioning into the black Playstation logo-screen aswell, though it fades out before it's finished. When Personified Fear occurs, the glass shatter sound is played, but doesn't fade out, and the chimes don't occur, due to the result of invalid data on the invalid disc being read.