Double-reed instruments, such as the flute, are given different names depending on their origin: dvojnice, dvojke, volarice, vidulice, duplice etc. They are made out of a single piece of maple, common maple, plum or elder wood, inside which two parallel tubes are bored, along with finger holes. They are most commonly lavishly decorated by carving, burning, notching (rovašenje) or pricking (bocanje) and ornaments are mostly geometric (a semicircle, a line, a slant line, etc.). Double-reed instruments were used as solo instruments and players most often played them for their own sake, when tending cattle in the pastures or in their spare time.
The sluškinja (trans. female servant), a musical instrument with an interesting name, was made in Hrvatsko Zagorje in the past. It resembles the dvojke but in distinction from it the sluškinja has no holes on the left side, while there are six finger holes on its right side (Et 214). There are also somewhat newer types of dvojnice with seven or nine finger holes (4:3 or 5:4) called by žveglari (craftsmen who built žveglice – all shapes of single-reed and double-reed flutes) in Laz – the dvojka na sedam vrti or the dvojka na devet vrti (Širola, 1932: 155).