MUSIC!
HRtP: Stage- Eternal Shrine Maiden, Boss- Either Swordsman from a Distant Star or Angel Legend
SoEW: Stage- Eastern Record of a Sealing of an Oriental Demon~A Phantom's Boisterous Dance, Boss- Complete Darkness
PoDD: Vanishing Dream~Lost Dream
LLS: Stage- Either Witching Dream or Alice Maestra, Boss- Faint Dream~Inanimate Dream
MS: Stage- ALICE IN WONDERLAND, Boss- Grimiore of Alice
EoSD: Stage- Either Voile, the Magic Library or The Young Descendant of Tepes, Boss- Septette for a Dead Princess
PCB: Stage- Charming Domination, Boss- Either Bloom Nobly, Sumizone Cherry Blossom ~ Border of Life or Necrofantasia
IaMP: Night Falls~Evening Star
IN: Stage- Retribution for the Eternal Night~Imperishable Night, Boss- Gensokyo Millenium~History of the Moon
PoFV: Either Spring Lane~Colorful Path or Wind God Girl
StB: Tengu is Watch~Black Eyes
MoF: Stage- The Primal Scene of Japan the Girl Saw, Boss- Faith is For the Transient People
SWR: Either Catastrophe in Bhavaagra~Wonderful Heaven or Bhavaagra As Seen Through a Child's Mind
SA: Stage- Either Heartless Fancy or Hellfire Mantle, Boss- Solar Sect of Mystic Wisdom~Nuclear Fusion
UFO: Stage- Interdimensional Voyage of a Ghostly Passenger Ship, Boss- Either Emotional Skyscraper~Cosmic Mind or Heian Alien
Soku- Unknown X~Unfound Adventure
DS- Bell of Avici~Infinite Nightmare
GFW- Stage- A Midnight Fairy Dance, Boss- Magus Night
TD- Stage- Either Desire Drive or Starry Sky of Small Desires, Boss- Either Old Yuanxian or Shoutoku Legend~True Administrator
HM- Either Emotional Skyscraper~Cosmic Mind, Futatsuiwa from Gensokyo, or Thus Dull World's Unchanging Pessimism
DDC- Title*- Mysterious Exorcism Rod, Stage- Bamboo Forest of the Full Moon, Boss- Dullahan Under the Willows
* DDC is probably the only case besides HM where my favorite song is the title theme.
And I've heard every single title, stage, and boss theme from every game. So a lot of these choices were tough.