All Pokémon on the field when Perish Song is used gain a perish count, except Pokémon with the AbilitySoundproof and Pokémon that already have a perish count. Starting at 4 on the turn Perish Song is used, the perish count decreases by 1 at the end of each turn (including the turn Perish Song is used in). When a Pokémon's perish count reaches 0, it faints.
If an affected Pokémon switches out with Baton Pass, the perish count will be transferred to the Pokémon switched in, even if it has the Ability Soundproof. If it switches out in any other way, neither it nor the switched-in Pokémon will have a perish count.
In Rotation Battles, if the Pokémon is rotated out, the perish count remains but does not decrease until it is rotated back in.
Perish Song can also be used as part of a Pokémon Contest combination, with the user gaining extra two appeal points if either the move Mean Look or Sing was used in the prior turn. It is also part of a Contest Spectacular combination, with the user gaining extra three appeal points if any of the moves Block, Mean Look or Spider Web was used in the prior turn.
If the perish count of multiple Pokémon on the field reaches 0 at the end of a turn, they will faint simultaneously (but messages and animations show up one after another).
Generation III onwards
If the perish count of multiple Pokémon on the field reaches 0 at the end of a turn, they will now faint in the same order they would move in.
If powered up with a Normalium Z into Z-Perish Song, all of the user's lowered stats are reset.
Any Pokémon in the player's Rescue Party affected by Perish Song will faint in 3 turns. However, it can be prevented by entering the stairs to the next floor or by sending home an affected partner before the third turn. It can also be prevented via any move, Ability, or item that heals all status effects (as opposed to a particular status effect), such as Heal Bell, Shed Skin, or a Heal Seed.
The move could refer to the tritone, a musical interval also known as Diábolus in musica (devil in the music), since it was believed when it was used, the devil got into the notes, this explains why the movement made the effect of weakening after three turns and what name and what is in the animations the notes change color to black.