Resonance tuning and glottal behaviour in different vocal qualities in Bulgarian women's singing. A pilot study

Bulgarian folk music usually involves women as singers and men as instrumentalists. It is often performed outdoors, where high levels of radiated vocal power are preferred. Two singing productions can be distinguished, which differ by their perceived loudness and timbre. The louder, more projected sound is labelled as /teshka/ (meaning /heavy/), and it tends to be used more in slower, sadder songs. The gentler, more lyrical sound is labelled as /leka/ (meaning /light/), and to some extent it shares timbral similarities with the classical or "head" voice used in Western European singing. What are the differences between these two Bulgarian singing productions, what are their common characteristics, and how do they differ from the classical "head" voice production?