Jigoku Rock is a banger of a rock track that plays whenever someone's being taken to Hell, generally when the overtly scary parts of their Afterlife Antechamber show themselves. The choir is there to let you know someone is going to Hell.
Jigoku Nagashi, an eerie yet determined track that practically radiates Tranquil Fury as Ai rides forth to claim a soul.
Jigoku no Kawa Nagare is a sad nautical theme that plays as Ai ferries a soul to whatever ironic torment awaits them.
Ake ni Somaru is a mocking One-Woman Wail that plays when Ai's clients don't think things can get any worse, but they still somehow mange to.
Jigoku Shonen might be the theme of a terminally arrogant one-off character, but damn if Gil de l'Enfer doesn't make the most of this rock melody.
Soushou is gives off a palpable sense of Tranquil Fury at the world's injustices, played over the first season's opening narration.
Kumo to Rouba to Shoujo, the sunset world's theme, is a sad piece used to give a sense of sympathy for the situations of both Ai's clients and Ai herself.
Ankoku Illusion is a dark theme that plays as Ai's minions show their spooky side to torment the villain of the week.
Ouma ga Toki is an eerie string piece that shows off the more mysterious side of the Hell Correspondence.
Kakugo is a desperate-sounding track that plays when Ai's clients finally decide to pull the thread because their tormentor has finally crossed the line.
Shibata Hashiru underscores Hajime's desperation to find Tsugumi after she runs away in the wilderness.
Mangetsu is perhaps the most heartwarming One-Woman Wail ever composed, reflecting Sentaro's lasting friendship with Ai. It later plays over the scene where Ren declares that he sees Ai and the other minions as family.
Sakura Fubuki is a furious-sounding theme that plays when Ai decides to finally avenge her own grudge and cuts loose with her hellish powers.
Sakura Uta plays when Ai finally lets go of her vengeance, a sad piece whose crescendo gives a sense of long-awaited relief.
Season 2 (Futakomori)
Jigoku Metal joins "Jigoku Rock" as one of the pieces that sometimes plays when Ai's minions send someone to Hell. It's a faster-paced theme that uses a rock track to accentuate a more intense choir.
Jigoku Ezu is another going-to-hell theme where Ai's minions drop all pretense of subtlety. Fittingly, it uses the same musical elements from Jigoku Metal more forcefully from the get-go.
Suimen no Tsuki is a mournful-sounding piece that represents Ai's clients' slow descent toward despair.
Aizome is the second season's credits theme, once again sung by Mamiko Noto. It even has a piano version that plays at the end of an episode when Ai's clients are (usually) finally able to move on with their lives, but the specter of what they just agreed to will follow them forever.
Annyui Shi Wara is a smooth, jazzy piece that reflects the lives Ai's minions have now.
San Kanae is a sad, yet determined piece that plays when Yuzuki encounters Ai for the first time. It also has a rock version.
Kakugo 2008 is this season's string-pulling theme. It sounds noticeably angrier than its predecessors, fitting with the often pettier reasons why people in this season turn to the Hell Correspondence.
Uka is a triumphant-sounding melody that plays when Ai emerges from Yuzuki to claim a soul. It's a She's Back moment in musical form.
Koigokoro is a happy theme that plays when the Victim Of T He Week still is still relatively carefree and hasn't had their life turned upside down by the episode's antagonist.
Zannen Waltz is a mocking waltz that plays during various reveals.
Hitori Asobi is a sadder version of "Kumo to Rouba to Shoujo", reflecting the rough lives that Yuzuki and Ai both had.
Imawasashii Jiken is a frantic piece that plays when Yuzuki goes a little too far and nearly pays the price for it.
Ai's theme is a beautiful remake of "Sakura Uta" that plays during the finale and at the end of Yamawaro's Character Focus episode.
Season 4 (Yoi no Togi)
While Yoi no Togi mostly re-uses music from the past three seasons, Michiru's themes express her situation incredibly well.
is a banger of a rock track that plays whenever someone's being taken to Hell, generally when the overtly scary parts of their Afterlife Antechamber show themselves. The choir is there to let you know someone is going to Hell.