Opera in the 20th Century

Some Ionarts readers have responded to my question about what operas should be covered in a course on Opera in the 20th Century, which I will be teaching this fall. Here is what readers have selected so far, with those operas I had not yet thought to include in the course in boldface type:

• Britten, Peter Grimes
  
• Stravinsky, The Rake's Progress
  
• Berg, Wozzeck and Lulu
  
• Schoenberg, Moses und Aron
  
• Corigliano, The Ghosts of Versailles
  
• Lloyd Webber, Evita
  
• Janáček, Jenůfa and The Cunning Little Vixen
  
• Menotti, The Old Maid and the Thief, The Consul, The Medium, Amahl and the Night Visitors
  
• Floyd, Susannah
  
• Strauss, Salome and Elektra
  
• Gershwin, Porgy and Bess
  
• Glass, Einstein on the Beach and Akhnaton
  
• Adams, Nixon in China
  
• Bartók, Bluebeard's Castle
  
• Debussy, Pelléas et Mélisande
  
• Birtwhistle, The Mask of Orpheus
  
• Ligeti, Le Grand Macabre
  
• Messiaen, Saint François d'Assise
  
• Meredith Monk, Atlas
  
• Stockhausen, Light: Seven Days of the Week (Licht cycle)
  
• Schnittke, Faust and Life with an Idiot
  
• Karetnikov, Till Eulenspiegel
  
• Ullmann, Der Kaiser von Atlantis
  
• Braunfels, Die Vögel (The Birds)
  
• Hindemith, Mathis der Maler, Murder, Hope of Women, or Das Nusch-Nuschi
  
• Robert Ashley, Atalanta (Acts of God) or Dust
  
• John Moran, The Manson Family
  
• Shostakovich, Lady Macbeth of the Mtensk District
  
• Prokofiev, Love for Three Oranges
  
• Poulenc, Dialogue des Carmélites
  
• Puccini, Tosca, Madama Butterfly, Turandot

That's already a pretty impressive list, too long to cover in a semester. However, if you know an opera that has scandalously been left off this list of the most important operas of the 20th century, you can still add it in the Comments section. Readers are also welcome to begin offering suggestions to pare down this list: what really HAS to be covered?