Basically all non-spook/scary ambient music in Minecraft gets replaced with spookier tunes either from base-game, Minecraft Dungeons, Minecraft Halloween Mash Up Pack 2015, spooky remixes from minecraft fans, or from royalty free music (cause I could only find so many spooky tunes before I would have to repeat what I already had and end up being redundant). With the specific selection if should hopefully be streamer safe for those who want to stream minecraft with just a pinch of spice. Modpack makers etc. if for some reason you need this musicpack, you're plenty free to use it.

here is the specifics on what was replaced (I will format the list and give links to said osts later)

replaced nether2 (Dead Voxel) with Nether 1 from Halloween Mash Up Pack
replaced nether3 (Warmth) with Nether 2 from Halloween Mash Up Pack
replaced end (The End- from base-game) with The End from Halloween Mash Up Pack
replaced calm1 with The End from base-game
replaced calm2 with Halloween 1 from Halloween Mash Up Pack
replaced calm3 with Halloween 2 from Halloween Mash Up Pack
replaced hal1 with Halloween 3 from Halloween Mash Up Pack
replaced hal2 with So Below from base-game (Nether Update specifically)
replaced hal3 with Graveyard from MC Dungeons
replaced hal4 with Soggier Cave from MC Dungeons
replaced nuance1 with Redstone Mines from MC Dungeons
replaced nuance2 with Thirteen from base-game
replaced piano1 with End Shrine from MC Dungeons: Echoing Void
replaced piano2 with Minecraft Theme Song But Scary (Remix) by TheGamerNerd
replaced piano3 with A Calm But Suspenseful Horror Soundtrack by Marc v/d Meulen
replaced piano4 with Broken Piano by VIVEK ABHISHEK
replaced menu1 with Halloween Menu from Halloween Mash Up Pack
replaced menu2 with Creeper Woods from MC Dungeons
replaced menu3 with Concrete Halls from base-game
replaced menu4 with The End from Halloween Mash Up Pack
Added Ghosts in The Tower for the boss track

Halloween Ambient Musicpack