My list will be made up of some pretty obscure recordings, comprised of: prog, jazz, and classical (mostly from the mid 20th century up through the present era).
My numbering got screwed up, but I believe there are 100.
Problem with list like these, since there are so many more pieces of music, that I consider at the same level as these, ask me a different day, and quite a few of these would be different.
Prog:
1) Yes - Close to the Edge
2) King Crimson - Larks’ Tongues in Aspic
3) Genesis - The Lamb Lies Down on Broadway
4) Banco del Mutuo Soccorso - Io Sono Nato Libero
5) National Health - Of Queues and Cures
6) PFM - Per un Amico
7) Magma - K.A (Köhntarkösz Anteria)
8) Arti e Mestieri - Tilt
9) Gentle Giant - In a Glass House
10) Änglagård - Hybris
11) Thinking Plague - In Extremis
12) Henry Cow - Western Culture
13) Univers Zero - Uzed
14) Hatfield and the North - S/T
15) Area - Arbeit Macht Frei
16) Eskaton - 4 Visions
17) Yes - Relayer
18) King Crimson - Red
19 ) Banco del Mutuo Socorrso - Darwin!
20) Il Balletto di Bronzo - YS
21) Pain of Salvation - Remedy Lane
22) Gentle Giant - Octopus
23) Deus Ex Machina - Equilibrismo da Insofferenza
24) Anglagard - Viljans Öga
25) Museo Rosenbach - Zarathustra
26) Echolyn - ...as the World
27) IQ - The Road of Bones
28) Art Zoyd - Symphonie Pour Le Jour Où Brûleront Les Cités
29) Frank Zappa - One Size Fits All
30) ELP - Brain Salad Surgery
31) PFM - Storia di un Minuto
32) Magma - Mekanïk Destruktïw Kommandöh
Genesis - Selling England by the Pound
Echolyn - Suffocating the Bloom
Le Orme - Felona e Sorona
Van Der Graaf Generator - Pawn Hearts
Van Der Graaf Generator - Godbluff
Camel - Mirage
Magma - Ëmëhntëhtt-Ré
Jazz:
33) Mahavishnu Orchestra -Inner Mounting Flame
34) John Coltrane - A Love Supreme
35) Oregon - Out of the Woods
36) Return to Forever - Romantic Warrior
37) Weather Report - Black Market
38 ) Anthony Braxton - Six Compositions: Quartet
39) The Art Ensemble of Chicago - Urban Bushman
40) Brand X - Unorthodox Behavior
41) Ralph Towner - Solo Concerts
42) Eberdard Weber - Cholours of Chloe
43) John Abercrombie - Timeless
44) Mahavishnu Orchestra - The Lost Trident Sessions
45) Szobel - Szobel
46) McCoy Tyner - The Real McCoy
47) Alice Coltrance - Ptah, The El Daoud
48) Pharaoh Sanders - Karma
49) Kemasi Washington - The Epic
50) Keith Jarrett - Koln Concerts
51) Allan Holdsworth - Metal Fatigue
52) Miles Davis - Sketches of Spain
53) Miles Davis - Bitches Brew
54) Bruford - One of a Kind
55) Terje Rypdal - Whenever I Seem to Be Far Away
56) Steve Coleman and the Five Elements - The Sonic Language of Myth
57) Steve Coleman’s Natal Eclipse - Morphogenesis
58) Ralph Towner - Solstice
59) Allan Holdsworth - I.O.U.
Oregon - Roots in the Sky
Iceberg - Sentiments
Miles Davis - In a Silent Way
Weather Report - Heavy Weather
John Coltrane - Ascension
Dave Holland - Conference of Birds
The Art Ensemble of Chicago - People of Sorrow
McCoy Tyner - Sahara
Anthony Braxton - 4 Compositions: Quartet
Classical:
60) Elliott Carter - Concerto for Orchestra
61) Elliott Carter - Variations for orchestra
62) Elliott Carter - Piano Concerto
63) Charles Wuorinen - 4th Piano Concerto
64) Charles Wuorinen - Iridule – 2006, for oboe and six players
65) Joan Tower - Concerto for Orchestra
66) Joan Tower - Silver Ladders
67) Alban Berg - Violin Concerto
68) Bruno Maderna - 3rd Oboe Concerto
69) Charles Wuorinen - Microsymphony
70) Unsuk Chin - Violin Concerto No. 1
71) Krzysztof Penderecki - Violin Concerto No. 2: Metamorphosen
72) Ernst Krenek - Static and Ecstatic
73) Joseph Schwantner - Percussion Concerto
74) Milton Babbitt - Composition for 12 instruments
75) Milton Babbitt - Concerti for Orchestra
76 ) Magnus Lindberg - Concert for Orchestra
77) Magnus Lindberg - Piano Concerto
78) Arnold Schoenberg - Variations for Orchestra
79) Bartok - Music for percussion, strings, and celesta
80) Samuel Barber - Piano Concerto
81) Stravinsky - Rite of Spring
82) Augusta Read Thomas - Eos: Goddess of Light
83) Harrison Birtwistle - Earth Dances