A Not Quite Complete List of Sidelong Studio Tracks by UK Prog Artists, 1966-1979 (Minimum 18 Minutes)

With a couple unique live recordings and prog-related stuff thrown in for good measure:

1966:
AMM: Later, During a Flaming Riviera Sunset 21:07
AMM: After Rapidly Circling the Plaza 23:19
1969
Deep Purple: First Movement: Moderato-Allegro 19:21
Deep Purple: Second Movement: Andante 19:11
George Harrison: Under the Mersey Wall 18:43
George Harrison: No Time or Space 25:05 
The Jody Grind: One Step On 18:44 
1970:
Egg: Symphony No. 2 23:53
Ginger Baker’s Air Force: Doin’ It 43:48
Ginger Baker’s Air Force: Doin’ It 31:54
Magna Carta: Seasons 22:20
Pentangle: Jack Orion 18:38
Pink Floyd: Atom Heart Mother 23:40
Rare Bird: Flight 19:38
Soft Machine: Facelift 18:46
Soft Machine: Moon in June 19:08
Soft Machine: Out-Bloody-Rageous 19:14 
T.2.: Morning: 21:12
1971:
Anthony Moore: Jam Jem Jim Jom Jum 21:23
Caravan: Nine Feet Underground 22:43
Centipede: Septober Energy (Part One) 21:43
Centipede: Septober Energy (Part Two) 23:35 
Centipede: Septober Energy (Part Three) 21:21
Centipede: Septober Energy (Part Four) 18:46
Egg: Long Piece No. 3 20:42 
Emerson Lake & Palmer: Tarkus 20:42
Jan Dukes de Grey: Sun Symphonica 18:57 
King Crimson: Lizard 23:26 
Neil Ardley: A Symphony of Amaranths (Part One) 24:11
Neil Ardley: A Symphony of Amaranths (Part Two) 22:33
Pink Floyd: Echoes 23:29
UFO: Flying 26:30
UFO: Star Storm 18:55
Van der Graaf Generator: A Plague of Lighthouse Keepers 23:13
Warm Dust: The Blind Boy, parts 1-5  18:20
1972:
Genesis: Supper’s Ready 23:06
Gracious!: Super Nova 21:43
Janus: Gravedigger 20:54
Jethro Tull: Thick as a Brick 22:40+21:10
Morgan: Nova Solis 20:16
Steamhammer: Penumbra 22:42
Yes: Close to the Edge 18:41
1973:
Byzantium: Something You Said (A Trilogy) 21:02
Capability Brown: Circumstances (In Love Past, Present, Future Meet) 20:52
Emerson Lake & Palmer: Karn Evil 9 29:41
Jethro Tull: A Passion Play 44:58
Man: C’mon 19:00
Man: Jam Up Jelly Tight/Oh No Not Again (Spunk Rock ‘73) 21:05
Mike Oldfield: Tubular Bells 25:33+23:17
Morgan: What Is/Is What 19:56
Nektar: Remember the Future (Part Two) 19:00
Yes: The Ancient (Giants Under the Sun) 18:37
Yes: Ritual (Nous Sommes du Soleil) 21:34
Yes: The Revealing Science of God (Dance of the Dawn) 20:26
Yes: The Remembering (High the Memory) 20:36
1974:
Gryphon: Midnight Mushrumps 18:56
Mike Oldfield: Hergest Ridge 21:29+18:46
Refugee: Credo 18:26
Rick Wakeman: The Journey - Recollection 21:06
Rick Wakeman: The Battle - The Forest 18:57
Yes: The Gates of Delirium 21:54 
1975:
Fripp & Eno: An Index of Metals 28:45
Hatfield & the North: Mumps 20:31
Mandalaband: Om Mani Padme Hum 20:51
Mike Oldfield: Ommadawn 19:24+13:55
Renaissance: Song of Scheherezade 24:40 
1976:
Van der Graaf Generator: Meurglys III (The Songwriter’s Guild) 20:51
1977:
Throbbing Gristle: The Original Soundtrack of Coum Transmissions Film of ‘After Cease to Exist’ 20:10
Keith Emerson: Piano Concerto No. 1 18:17 
1979:
Sky: Where Opposites Meet 19:19 

Every Great Song Ever’s UK Prog Series So Far:

Volume One: Mix.  Notes
Volume Two: Mix. Notes
Volume Three: Mix.  Notes
Volume Four: Mix.  Notes.  
Volume Five: Mix.  Notes.  
Volume Six: Mix.  Notes
Volume Seven: Mix.  Notes.  
Volume Eight: Mix.  Notes.  
Volume Nine: Mix.  Notes.   
Volume Ten: Mix.  Notes.   
Volume Eleven: Mix.  Notes.   
Volume Twelve: Mix. Notes
Volume Thirteen: Mix. Notes
Volume Fourteen: Mix. Notes