Boss Music

Boss Music is used numerous times in the Kingdom Hearts series to indicate that the current battle is with a boss. Most Boss Music is fast-paced and sends a theme of evil or tension. Usually the same song would be used in different boss battles to show the connection between them, i.e Shrouding Dark Cloud is associated with Heartless Bosses and Squirming Evil is used commonly for Disney Bosses in Kingdom Hearts.

Awakening

 * Darkside - Dive into the Heart (Destati)

Destiny Islands

 * Darkside - Destiny's Force

Traverse Town

 * Leon - Night of Fate


 * Guard Armor - Shrouding Dark Cloud


 * Opposite Armor - Destiny's Force

Wonderland

 * Queen of Hearts, Card Soldiers and Crank Tower - To Our Surprise


 * Trickmaster - Shrouding Dark Cloud

Olympus Coliseum

 * Cloud (Story) - Shrouding Dark Cloud


 * Cerberus (Story) - Squirming Evil


 * Hades - Squirming Evil


 * Rock Titan - The Deep End


 * Ice Titan - The Deep End


 * Sephiroth - One-Winged Angel (from Final Fantasy VII)

Deep Jungle

 * Sabor - Having a Wild Time


 * Clayton and Stealth Sneak - Squirming Evil

Agrabah

 * Pot Centipede - Shrouding Dark Cloud


 * Cave of Wonders Guardian - Arabian Dreams


 * Jafar (1st Battle) - Squirming Evil


 * Jafar (Genie) - Destiny's Force


 * Kurt Zisa - The Deep End

Monstro

 * Parasite Cage (1st Battle) - Shrouding Dark Cloud


 * Parasite Cage (2nd Battle) - Destiny's Force

Atlantica

 * Ursula - Squirming Evil


 * Giant Ursula - The Deep End

Halloween Town

 * Lock, Shock and Barrel - Spooks of Halloween Town


 * Oogie Boogie (1st Battle) - Squirming Evil


 * Oogie Boogie (2nd Battle) - Destiny's Force

Neverland

 * AntiSora - Shrouding Dark Cloud


 * Captain Hook - Squirming Evil


 * Phantom - Destiny's Force

Hollow Bastion

 * Riku (1st Battle) - Scherzo Di Notte


 * Maleficent (1st Battle) - Squirming Evil


 * Maleficent (Dragon) - The Deep End


 * Riku (2nd Battle) - Forze del Male


 * Behemoth - Destiny's Force

Bald Mountain

 * Chernabog - A Night on the Bald Mountain

End of the World

 * Ansem (1st Battle) - The Deep End


 * Darkside - Destiny's Force


 * Ansem (2nd Battle) - Forze del Male


 * World of Chaos - Guardando Nel Buio

Hollow Bastion

 * Unknown - Disappeared

Traverse Town

 * Guard Armor - Struggle Away

Wonderland

 * Card Soldiers - To Our Surprise


 * Trickmaster - Struggle Away

Olympus Coliseum

 * Cloud - Go For It!


 * Hades - The Fight for my Friends

Agrabah

 * Jafar - The Fight for my Friends

Monstro

 * Parasite Cage - Struggle Away

Halloween Town

 * Oogie Boogie - The Fight for my Friends

Atlantica

 * Ursula - The Fight for my Friends

Neverland

 * Captain Hook - The Fight for my Friends

Hollow Bastion

 * Maleficent - The Fight for my Friends

Destiny Islands

 * Darkside - Struggle Away

Simulated Twilight Town

 * Vexen (2nd Battle) - The 13th Struggle

Castle Oblivion

 * Axel (1st Battle) - The 13th Struggle


 * Larxene (1st Battle) - The 13th Struggle


 * Riku Replica (1st Battle) - The Force in You


 * Riku Replica (2nd Battle) - The Force in You


 * Vexen (1st Battle) - The 13th Struggle


 * Riku Replica (3rd Battle) - The Force in You


 * Riku Replica (4th Battle) - The Force in You


 * Larxene (2nd Battle) - The 13th Struggle


 * Axel (2nd Battle) - The 13th Struggle


 * Fake Marluxia (1st Battle) - Graceful Assassin


 * Marluxia (Second Form) (2nd Battle) - Scythe of Petals

Hollow Bastion

 * Maleficent - The Fight for my Friends

Traverse Town

 * Guard Armor - Struggle Away

Agrabah

 * Jafar - The Fight for my Friends

Monstro

 * Parasite Cage - Struggle Away

Neverland

 * Captain Hook - The Fight for my Friends

Wonderland

 * Trickmaster - Struggle Away

Olympus Coliseum

 * Hades - The Fight for my Friends

Atlantica

 * Ursula - Face It!

Halloween Town

 * Oogie Boogie - The Fight for my Friends

Destiny Islands

 * Darkside - Struggle Away

Simulated Twilight Town

 * Riku Replica (2nd Battle) - The Force in You

Castle Oblivion

 * Vexen - The 13th Struggle


 * Riku Replica (1st Battle) - The Force in You


 * Lexaeus - The 13th Struggle


 * Ansem - Revenge of Chaos

Castle Oblivion

 * Marluxia (Third Form) - Lord of the Castle

Destiny Islands

 * Zexion - The 13th Struggle

Awakening

 * Twilight Thorn - Tension Rising

Simulated Twilight Town

 * Axel (1st Battle) - The 13th Struggle


 * Axel (2nd Battle) - The 13th Struggle

Hollow Bastion

 * Demyx (2nd Battle) - The 13th Dilemma

Radiant Garden

 * Sephiroth - One Winged Angel (For Final Fantasy VII)

Land of Dragons

 * Shan Yu - Vim & Vigor


 * Storm Rider - The Corrupted

Beast's Castle

 * Possessor/Thresholder - Dance to the Death


 * The Beast - Tension Rising


 * Shadow Stalker - Dance to the Death


 * Dark Thorn - Desire for All That Is Lost


 * Xaldin - The 13th Dilemma

Underworld

 * Cerberus - Vim and Vigor


 * Demyx (1st Battle) - Tension Rising


 * Pete (1st Battle) - Rowdy Rumble


 * Hades - The Encounter

Olympus Coliseum

 * Hydra - Desire for All That Is Lost

Timeless River

 * Pete (Timeless River) - Rowdy Rumble


 * Pete (2nd Battle) - Rowdy Rumble


 * Pete (3rd Battle) - Desire for All That Is Lost

Port Royal

 * Captain Barbossa and Illuminator - Vim and Vigor


 * Grim Reaper (1st Battle) - Sinister Shadows


 * Grim Reaper (2nd Battle) - The Corrupted

Agrabah

 * Volcanic Lord and Blizzard Lord - Desire for All That Is Lost


 * Jafar - The Encounter

Halloween Town

 * Prison Keeper and Lock, Shock and Barrel - Dance to the Death

Christmas Town

 * Oogie Boogie - The Encounter


 * Lock, Shock and Barrel - Rowdy Rumble


 * The Experiment - The Corrupted

Pride Lands

 * Shenzi, Banzai, and Ed (1st Battle) - Rowdy Rumble


 * Scar - The Encounter


 * Shenzi, Banzai, and Ed (2nd Battle) - Rowdy Rumble


 * Groundshaker - The Corrupted

Space Paranoids

 * Hostile Program - The Corrupted


 * Sark - Sinister Shadows


 * Sark and the MCP -The Encounter

The World that Never Was

 * Xigbar - The 13th Dilemma


 * Luxord - The 13th Struggle


 * Saïx - The 13th Dilemma


 * Xemnas - Disappeared


 * Xemnas (Dragon) - Darkness of the Unknown


 * Xemnas (Dragon) (2nd Battle) - Darkness of the Unknown


 * Xemnas (Final) - Darkness of the Unknown

Kingdom Hearts

 * Xemnas (Armor) (1st Battle) - A Fight to the Death

The Gathering Place

 * Lingering Sentiment - Rage Awakened

Cavern of Remembrance

 * Xemnas Data Battles - Disappeared and Darkness of the Unknown


 * Xigbar, Xaldin, Saïx and Demyx Data Battles - The 13th Dilemma


 * Vexen, Lexaeus, Zexion, Marluxia and Larxene Data Battles - The 13th Reflection


 * Axel and Luxord Data Battles - The 13th Struggle


 * Roxas Data - The Other Promise

The World that Never Was

 * Organization XIII - The Other Promise

Various

 * All Absent Silhouettes - The 13th Refection (Agrabah (Vexen), Twilight Town (Lexaeus), Underworld (Zexion), Beast's Castle (Marluxia), Port Royal (Larxene))

Twilight Town

 * Guardian - Tension Rising
 * Tailbunker - Tension Rising (this is the music for a lot of the "minor" Heartless bosses that barely qualify as boss fights)
 * Darkside -

Agrabah

 * Pete -
 * Antlion - Shrouding Dark Cloud

Beast's Castle

 * Dark Follower -
 * Infernal Engine -

Olympus Coliseum

 * Morning Star -
 * Guard Armor -

Wonderland

 * Lurk Lizard -

Never Land

 * Wavecrest -

Halloween Town

 * Leechgrave - Vim and Vigor? (Might be A Fight To The Death)

Various

 * Here there be spoilers?