The following are the assortment credits. 
Texture pack is based on 32-in-24-15-tex. Additions are credited by markers inside the WAD
If no sky is specified, the sky is from this pack
Most custom sprites are from Realm667 or other Id Tech games. 
Additional information is stated inside DECOHACK code lump.
All code is bespoke by ViolentBeetle

Project Lead: ViolentBeetle

Episode 1: The First Frontier

MAP01: Skullgate Horizon	
Author: Shawny
MIDI:  MtPain27 - Underdark

MAP02: Red Shell Station
Author: Death Bear
MIDI: Lunacy by Psyrus

MAP03: Silvershine Satellite
Author: DynamiteKaitorn	
MIDI: Lab Rat from Jazz Jackrabbit 2

MAP04: Radio Outpost 
Author: Moustachio	
MIDI: conveyor by Fookerton 

MAP05: Cygnus Terminal
Author: novaseer
MIDI: "Alien Activity" by novaseer (bespoke track)

MAP06: Starshipping Hub
Author: ViolentBeetle
MIDI: Kaleidoscopic Array by Mr. Freeze & Cammy

Episode 2: Industrial Devilution

MAP07: Technofear
Author: Merrick18818
MIDI: Death Come 4 - Chasing Devrich

MAP08: Static Gristle
Author: brxyz
MIDI: Boss 3 from Nightmare Creatures (sequenced by Darkholy Sephiro, original by Frédéric Motte)

MAP09: Boxed Inc. 
Author: donk konk
MIDI: Warehaus by Lee Jackson (Duke Nukem 3D)

MAP10: How It's Made
Author: Spammishh
MIDI: Rendition of "Wily Fortress 2" from Mega Man 7 (Jarel Jones)

MAP11: Rustwater Reclamation
Author: ViolentBeetle
MIDI: Hail the Severed Head by Lipphet
Sky: From Mek's Box o' Skies

MAP12: Red Dusk	
Author: DFF	
MIDI: SeeD Theme from FF8 (sequenced by QMA)

Episode 3: Accept Urban Decline

MAP13: More Fun Than Television
Author: ViolentBeetle
MIDI: Lord of L.A. by Robert Prince (Duke Nukem 3D)
Sky: TimelordSheep

MAP14: Lost in society
Author: Shawny
MIDI: Psychedelic Eyeball - lonesoul

MAP15: Ruins of Sanity
Author: MAN_WITH_GUN
MIDI: Corroded Ruins by Snaxalotl

MAP16:Mind the Gap
Author: brxyz
MIDI: Paint The Town Red by Jimmy Paddock

MAP17: Urban Flesh District
Author: CBM
MIDI: Danger by Roald Strauss (IndieGameMusic.com)

MAP18: High-Rise Showdown
Author: RobertF
MIDI: Kamikaze Marmite by James Paddock

Episode 4: Ancient History

MAP19: Wasteland Kingdom
Authors: MajaMystic256 & ViolentBeetle
MIDI:  The Incessant Flow of Time by Stuart Rynn
Sky: Mek's Box 'o skies

MAP20: Yacumana
Author: DFF
MIDI: Return of the Troubles by Jeremy Doyle

MAP21: Apophis
Author: RobertF
MIDI: Horus by Jeremy Doyle

MAP22: Deep Under Layla
Author: wen
MIDI: Dark Angel by Jimmy

MAP23: Sacred Geometry
Author: Jark
Midi 1: Alone in Hell by MFG38
Midi 2: Gestation by Immorpher

MAP24: Burnt Offerings
Author: novaseer
MIDI: The Hour Approaches by novaseer (bespoke track)

Episode 5: Helludal Society

MAP25: Tender Flesh 
Author: Beubeu
MIDI: Bloody Skies by Psychedelic Eyeball

MAP26: Fragments of Resolution
Author: myolden
MIDI: False Paradise by Jimmy

MAP27: Red Sabbath
Author: ViolentBeetle
MIDI: Cathedral Rock by Jimmy
Sky: Based on painting by Yang Xueguo and Mek's box o' Skies

MAP28: In Search of the Secret Fire
Author: FlyingGoner
MIDI: Pollutants by James Paddock, from Flashback to Hell

MAP29: Lasting Lights of The Dying Sun
Author: MAN_WITH_GUN 
MIDI: Racharacharach by Ribbiks
Minor tweaks, must remember difficulty settings

MAP30: Slayer and the Beasts
Author: Shawny
MIDI: Crushed Spirits by pcorf

Episode 6: The Final Frontier

MAP31: The Whooshmaster
Author: Doomy__Doom
MIDI: Jump is not allowed by Korp
Sky: Box o' Skies

MAP32: One Small Step
Author: dac
MIDI: rustybridge.mid by Stuart Rynn
MAP33: Omen of Algol
Author: RobertFMIDI: Arrival by AD_79
Sky: Based off Mek's Box o'skies and default sky

MAP34: A Giant Leap
Author: dac	
MIDI: Mech' by Psyrus

MAP35: Abysswatch
Author: ViolentBeetle
MIDI: Eternal Damnation by  Knightrider of Doom (From AV MIDI pack)

Intermission MIDI: Stomping onto the Beaten Path by UUN4
STBAR: by brxyz