How does the Norwegian Hardanger fiddle produce its distinctive sound?

The Norwegian Hardanger fiddle, or hardingfele, produces its distinctive, bright, and silvery sound primarily through the use of sympathetic strings.1

While the instrument features four bowed strings played similarly to a standard violin, it is uniquely constructed with an additional four or five metal sympathetic strings positioned beneath them. These sympathetic strings are not played directly; instead, they vibrate in response to the bowed strings. This resonance reinforces the upper harmonics of the notes being played, which creates the instrument's characteristic shimmering timbre.231

As with other stringed instruments, the overall sound quality is also influenced by the instrument's resonating body, which amplifies and colors the vibrations produced by the strings.1