This article presents the results of field research carried out in Bulgaria. The subject of the study was multipart female singing in the Shops region. Analysis of the seasonal ceremonial songs focuses on vocal sounding, its psycho-acoustic and physiological aspects, musical structures and cultural context. Special attention was paid to local terminology used by folk singers who can also tell about musical construction and ways of performing. Antiphonal singing is predominantly diaphonic on the background of the bourdon. The voices are divided into leading and accompanying parts and are strictly organized as to the number of singers and their location. The pitches are sometimes shaky, the singers used to rough-sounding intervals, in particular seconds. The seconds are intentionally intoned so as to experience the acoustic properties of this interval known elsewhere as 'dissonance'. The performers have a predilection for shrill vocal timbres and for high dynamic levels. Specific manners of performance include advanced melismatic ornamentation and closing exclamations. Musical articulation seems to be more important than clear pronunciation of the text. The singers make the most even of the phonic qualities of the words so as to gain the desired musical and expressive value. Multipart singing in the investigated region is a highly complex and dynamic phenomenon. There is no single criterion by which to classify these songs.