Kristoff supplemented his singing with music from his lute.
One of Kristoff's possessions is a lute.
History[]
As Kristoff and Sven settled down for the night in a barn next to Wandering Oaken's Trading Post and Sauna, the ice harvester sung a lullaby and used his lute as an accompaniment.
While traveling to the North Mountain, Anna used the lute as a makeshift weapon to defend Kristoff's sled from an attacking wolf. The lute was ultimately lost when Anna, Sven, and Kristoff were forced to abandon the sled upon encountering a gorge, though the princess promised to replace everything lost. True to her word, Anna gave Kristoff a new lute along with his new sled.
During Christmas, Kristoff played his new lute as he sang his tradition to Anna and Elsa in hopes of cheering the sisters up after the citizens had departed.