It also has an old and rich tradition of choral singing.

An excerpt from the article 34 facts about Bulgaria

One of the most famous Bulgarian medieval artists is John Koukouzelis, the creator of the so-called neo-Byzantine musical notation. Today's famous Bulgarian singers, who are among the world's best, and often perform in the best opera houses across Europe, include Boris Hristov, Nikolai Giaurov, and Nikola Giuzelev.