The nyckelharpa is a traditional Swedish string instrument that dates back to the 14th century. It features a wooden body, a set of strings, and a series of keys that are pressed to change the pitch. The instrument is played with a bow, similar to a violin, and produces a unique, resonant sound that is often associated with Swedish folk music. Typically, the nyckelharpa has 16 strings, with some used for melody and others for accompaniment. It is an integral part of Swedish cultural heritage and has gained popularity in various folk music circles around the world, contributing to the revival of traditional music styles.