Music is not universally constructed or interpreted across cultures. Western art music is based on tertian harmony using intervals of thirds and equal temperament with the octave divided into twelve semitones. However, folk music from Eastern Europe, Asia, Africa, the Middle East, and indigenous groups often does not use this system and instead may divide the octave into other numbers of tones, such as the 24 microtones used in traditional Chinese music. Additionally, the emotional content conveyed by different musical systems and intervals varies cross-culturally.