Note the prevalent use of 2nds, not only on the Dvojnice but by two female singers in the first of these videos:
[youtube=http://www.youtube.com/playlist?list=PLDYUDRHuY5EJsLH-Edd86JOZHEV_hPbW6]
More info:
www.gajde.com/en/instrumenti/dvojnice-2/
www.metmuseum.org/collections/search-the-collections/502374
