Chant (čǽnt) music features repetitive sounds either sung or played on instruments. This music tends to use only one or two pitches that get repeated throughout the piece. Chants can be simple and repeat a melody, or they can be complex and feature lots of repeating phrases. Gregorian chant may be the most popular type of chant music, and it was originally made by Gregorian monks as a form of religious music. The music project Enigma, popular in the 1990s, used chant music in some of its songs. Instrumental chant music may feature one or several instruments playing repeating pitches. The sound created is full, and it will often sound like there are more instruments playing than are really used.