The Modern Era increased the amount of freedoms that was in music to unimaginable heights. Dissonance was greatly more prominent than what it was in any other time period. One ballet, "The Rite of Spring" caused riots because of the dissonance that was used. People thought that the composer, Igor Sravinsky, was attempting to destroy music. Mahler is one of the leaders of modern times. His music pushed the limits on range, keys, and harmonies in general. Mahler's symphonies could last hours and require extremely large orchestras. New instruments have been added and digital effects layered over existing instruments. Composers wrote music including some of these newer sounds. Music will continue to evolve and more era will be created, but for now, these are the periods of what we call "classical music."