History: Which of the following is not electronic music?

Which of the following is not electronic music?

• Musique concrète.
  This form of music combines real sounds with electronic techniques.
• String sonatas.
  While you might hear the music on speakers, electronic devices are not a primary sound source.
• Ambient music.
  Most ambient music uses synthesizers and samplers as primary sources.
• Electronic dance music.
  Electronic dance music, by definition, uses electronic devices as a primary source.