What is "isihia"

Isihia (, " hesychia") are a Bulgarian music band founded in 2000, the style of which unites elements of Bulgarian folklore and Hesychast Christian chant of the 14th century to create an atmosphere of Balkan spiritual mysticism. Many of the group's songs cover topics of the medieval history of Bulgaria, mostly the period of the Ottoman invasion of the Balkans and the attempts on its repulsion and the early Ottoman rule of Bulgaria, i.e. the 14th-15th century, but also other moments of hardship such as the tragic Battle of Klyuch of 1014.