Share '10 pieces to introduce 20th and Century music'

If you were introducing 20th century music to a friend, a class, or a to any just interested in Modern music and only had ten pieces to show a spectrum or shows a evolutionary time line of music from 1900- 1999. Pick ten pieces (operas, symphonies, chamber music, any complete pieces) that you think best represent the 20th century or that you think are the best ten pieces to introduce some one who…