The dvojnica is actually two pipes, two jedinkas made from one piece of wood, which can be played simultaneously. The music of the dvojnica is always two-part, usually in thirds, although other combinations between tones are also possible. Like most traditional instruments, the dvojnica is limited in its register of tones. One can play at most six sounds in a given octave. By blowing, it is sometimes possible to play certain tones in several octaves, but the intonation is usually not pure. It is interesting how the slanting of dvojnica towards the mouth of the player while playing can achieve an effect in which one side of the dvojnica plays in the normal and the other side in a higher octave.

The dvojnica was played in all parts of Croatia in different variants and under different names: dvojnica, žveglica, dipla, dvogrla, dvojkinja, vidalica, etc. In all of the regions of Croatia the dvojnica almost always had four to five holes for playing on its right side and three to four holes on the left side. Similar pipes in some parts of Bosnia and Herzegovina and Serbia had a reverse layout of holes, i.e. on the left side they had more than on the right side of the pipe. Also, dvojnicas from Croatia did not have reeds on the lower side, i.e. reeds turned towards the player. They were always placed upwards. The photographs below show dvojnicas from various regions of Croatia (Dalmatia, Slavonia, Croatian Zagorje, and Istria).