Arnold Schoenberg is generally credited with the invention of the notorious twelve-tone system. But Schoenberg wasn't necessarily the first composer to think of using all twelve notes available. Others flirted briefly with this approach to music, before Schoenberg systematized it in the 1920s. Charles Ives wrote an experimental sketch using twelve tones. Franz Liszt wrote a small "Bagatelle without a key" late in his life. And in the music we just heard, from the tone poem Thus Spoke Zarathustra, Richard Strauss created a fugue on a theme made up of all twelve pitches of the chromatic scale.