Magnum Opus

The term "magnum opus" is reserved for an artist's greatest achievement. In some cases, the artist, the public, and critics all agree upon the work that is worthy of such distinction; in others, it takes over 200 years before a consensus begins to emerge, informed by the composer's place in the repertoire; and in yet other cases, there is no consensus, and there need not be one. If you, however, are looking for one great work to introduce you to a composer, then you couldn't do much better than to refer to this list, which I compiled based on scrupulous research.

I must give credit to the editors at http://digitaldreamdoor.nutsie.com/pages/best-classic-top10.html. Their classical music lists are well-informed, and I agreed with nearly all of their 39 choices for a composer's "top work."

Adams, John - Nixon in China
Albeniz, Isaac - Iberia
Albinoni, Tomaso Giovanni - Oboe Concerto in D Minor, Op. 9, No. 2
Bach, Carl Philippe Emanuel - 6 Hamburg Symphonies, Wq. 182
Bach, Johann Sebastian - Mass in B Minor
Balakirev, Mily Alexeyevich - Tamara
Barber, Samuel - Adagio for Strings
Bartok, Bela - Concerto for Orchestra
Bax, Arnold - Tintagel
Beach, Amy Marcy Cheney - Symphony in E Minor "Gaelic"
Beethoven, Ludwig von - Symphony No. 9 "Choral"
Bellini, Vincenzo - Norma
Berg, Alban - Violin Concerto "To the Memory of an Angel"
Berio, Luciano - Sequenza I for Flute solo
Berlioz, Hector - Symphonie Fantastique
Bernstein, Leonard - Symphonic Dances from "West Side Story"
Berwald, Franz Adolf - Symphony No. 3 "Singuliere"
Bizet, Georges - Carmen
Boccherini, Luigi - String Quintet in E Major, Op. 11, No. 5
Borodin, Alexander - Symphony No. 2
Boulez, Pierre - Le marteau sans maitre
Brahms, Johannes - Symphony No. 4
Britten, Benjamin - War Requiem
Bruch, Max - Violin Concerto No. 1
Bruckner, Anton - Symphony No. 7
Buxtehude, Dietrich - Prelude, Fugue and Chaconne for Organ in C Major, BuxWV137
Byrd, William - My Ladye Nevells Booke
Cage, John - Sonatas and Interludes for Prepared Piano
Carter, Elliott - String Quartet No. 2
Chabrier, Emmanuel - Espana
Chausson, Ernest - Poeme for Violin and Orchestra
Chopin, Frederic - Preludes, Op. 28
Copland, Aaron - Appalachian Spring
Corelli, Arcangelo - Concerti grossi, Op. 6
Couperin, Francois - Pieces de clavicin, Book 3, Ordre 13 in B Minor
Debussy, Claude - La Mer
Delibes, Leo - Lakme
Delius, Frederick - On Hearing the First Cuckoo in Spring
Donizetti, Gaetano - Lucia di Lammermoor
Dowland, John - Lachrimae
Dufay, Guillaume - Mass "Se La Face ay pale"
Dukas, Paul - The Sorcerer's Apprentice
Dvorak, Antonin - Symphony No. 9 "From the New World"
Elgar, Edward - Cello Concerto in E Minor
Enescu, George - Romanian Rhapsodies
Falla, Manuel de - El amor brujo
Faure, Gabriel - Requiem
Franck, Cesar Auguste - Violin Sonata in A Major
Gabrieli, Giovanni - In Ecclesiis
Gershwin, George - Rhapsody in Blue
Gesualdo, Carlo - Madrigals, Book VI
Gibbons, Orlando - First Set of Madrigals and Mottets
Glass, Philip - Einstein on the Beach
Glazunov, Alexander - Violin Concerto in A Minor
Glinka, Mikhail - Russlin and Ludmilla
Gluck, Christoph von - Orpheus and Eurydice
Gorecki, Henryk - Symphony No. 3 "Symphony of Sorrowful Songs"
Gounod, Charles Francois - Faust
Grainger, Percy - Lincolnshire Posy
Granados, Enrique - Goyescas
Grieg, Edvard - Piano Concerto in A Minor
Handel, George Frideric - Messiah
Haydn, Franz Joseph - The Creation
Hildegard of Bingen - Symphonia armonie celestium revelationum
Hindemith, Paul - Mathis der Maler (Symphony)
Holst, Gustav - The Planets
Hummel, Johann Nepomuk - Piano Concerto No. 2
Ives, Charles - Three Places in New England
Janacek, Leos - Glagolitic Mass
Josquin Desprez - Missa Pange Lingua
Kabalevsky, Dmitri - The Comedians, for small orchestra (suite)
Khachaturian, Aram - Gayane
Kodaly, Zoltan - Hary Janos Suite
Korngold, Erich - Violin Concerto in D Major
Kreisler, Fritz - Liebesleid
Lalo, Edouardo - Symphonie espagnole
Lassus, Orlande de - Penitential Psalms of David
Lehar, Franz - Die lustige Witwe
Leoncavallo, Ruggiero - I Pagliacci
Leonin - Viderunt Omnes
Ligeti, Gyorgy - Atmospheres
Liszt, Franz - Piano Sonata in B Minor
Lully, Jean-Baptiste - Atys
Machaut, Guillaume de - Messe de Nostre Dame
Mahler, Gustav - Symphony No. 5
Martinu, Bohuslav - Double Concerto for 2 String Orchestras, Piano & Timpani
Mascagni, Pietro - Cavalleria Rusticana
Massenet, Jules - Werther
Mendelssohn, Felix - Midsummer Night's Dream Incidental Music
Messiaen, Olivier - Quartet for the End of Time
Meyerbeer, Giacomo - Les Huguenots
Milhaud, Darius - La Creation du Monde
Monteverdi, Claudio - Vespro della Beata Vergine
Mozart, Wolfgang Amadeus - Don Giovanni
Mussorgsky, Modest - Pictures at an Exhibition
Nielsen, Carl - Symphony No. 5
Offenbach, Jacques - The Tales of Hoffman
Pachelbel, Johann - Canon and Gigue in D Major
Paganini, Nicolo - Caprices for Solo Violin
Palestrina, Giovanni Pierluigi da - Missa Papae Marcelli
Part, Arvo - Tabula Rasa
Pergolesi, Giovanni Battista - Stabat Mater
Perotin - Beata Viscera
Piazzolla, Astor - Tango Suite for Two Guitars
Poulenc, Francis - Flute Sonata
Prokofiev, Sergei - Symphony No. 5
Puccini, Giacomo - La Boheme
Purcell, Henry - Dido and Aeneas
Rachmaninov, Sergei - Piano Concerto No. 2
Rameau, Jean-Philippe - Castor et Pollux
Rautavaara, Einojuhani - Cantus Arcticus "Concerto for Birds and Orchestra"
Ravel, Maurice - Daphnis et Chloe
Reger, Max - Introduction and Passacaglia in D Minor
Respighi, Ottorino - Pines of Rome
Rimsky-Korsakov, Nikolai - Scheherazade
Rodrigo, Joaquin - Concierto de Aranjuez
Rossini, Gioachino - The Barber of Seville
Saint-Saens, Camille - Symphony No. 3 "Organ"
Sarasate, Pablo Martin de - Zigeunerweisen
Satie, Erik - 3 Gymnopedies
Scarlatti, Domenico - Sonata in E, K.380, L.23 "Cortege"
Schnittke, Alfred - Concerto Grosso No. 1
Schoenberg, Arnold - Verklarte Nacht
Schubert, Franz - Winterreise
Schumann, Clara Josephine - Trio for Piano and Strings in G Minor
Schumann, Robert - Piano Concerto in A Minor
Schutz, Heinrich - Symphoniae Sacrae III, Op. 12
Scriabin, Alexander - Piano Sonata No. 5
Shostakovich, Dmitri - Symphony No. 10
Sibelius, Jean - Symphony No. 2
Smetana, Bedrich - Ma Vlast
Stockhausen, Karlheinz - Kontakte
Strauss, Johann, Jr. - The Blue Danube Waltz
Strauss, Richard - Till Eulenspiegel's Merry Pranks
Stravinsky, Igor - The Rite of Spring
Tallis, Thomas - Spem in alium
Tchaikovsky, Pyotr Ilyich - Symphony No. 6 "Pathetique"
Telemann, Georg Philipp - Overture-Suite for Recorder, Strings and Basso Continuo in A Minor, TV 55 no a 2
Tippett, Michael - A Child of Our Time
Vaughan Williams, Ralph - Fantasia on a Theme of Thomas Tallis
Verdi, Giuseppe - Otello
Victoria, Tomas Luis de - O Magnum Mysterium
Villa-Lobos, Heitor - Bachianas Brasileiras No. 5
Vivaldi, Antonio - Four Seasons
Wagner, Richard - Tristan und Isolde
Walton, William - Symphony No. 1
Weber, Carl Maria von - Der Freischutz
Webern, Anton - Five Movements for String Quartet
Wieniawski, Henryk - Violin Concerto No. 2
Wolf, Hugo - Morike Lieder

I welcome comments challenging the works I've decided to include here.