Diple, dvojnice, or dvojanke (pluralia tantum; pronounced dîple̞, dʋǒ̞ːjnit͡se and dʋǒ̞jaːŋke̞) are a traditional woodwind musical instrument in Croatian, Montenegrin and Serbian music.
The diple may be found as a fipple

Fipple

A fipple is a constricted mouthpiece common to many end-blown woodwind instruments, such as the tin whistle and the recorder. These instruments are known variously as fipple flutes, duct flutes, or tubular-ducted flutes.-How it works:...

 flute or as a reedpipe, but in either case is distinctive in that it incorporates two bores within one body, and thus creates two notes simultaneously.