The instrument has two parts, a round metal loop with two protruding arms, with a thin steel tongue or spring fastened between running lengthwise. To produce sound, the player presses the metal arms against the teeth by holding the loop, and strikes the tongue or spring with a finger. The mouth acts as a resonance chamber which can vary the instrument's pitch, creating tones in the overtone series.

The munnharpe has maintained itself in living tradition mainly in the area of Setesdal, but the instrument has also been popular in Hallingdal and Valdres. One can play a varied repertory on the munnharpe, but the instrument has mostly been used to play dance tunes.