Stabule

Stabule, also known as stebule or stabuļa, is a Latvian woodwind instrument made from various materials like wood, bark, and reeds.

It consists of a tube with a whistle and finger holes, typically producing a diatonic scale.

[1] The name can apply to variety of wind instruments, but in general sense it is a pipe with 4-8 finger holes.

A similar more simple type of stabule without finger holes can be made from willow bark.

The plug is generally meant for tuning the stabule, but sometimes also used as a slide to adjust tone while playing.