Anonymous 4 is a female a cappella quartet, based in New York City. Their main performance genre is medieval music, although they have also premiered works by living composers such as John Tavener and Steve Reich. Anonymous 4 has performed in cities throughout North America, and have been regulars at major international festivals. Their cds have sold almost 2 million copies worldwide. The name of the group is a pun on the name of an anonymous English music theorist of the late 13th century