The Harolina is a stringed musical instrument. The strings are either plucked or strummed like a guitar. Tarquin Longleap Woodsorrel has so far been the only character to play one.
Tarquin Woodsorrel was an expert with the harolina and played it as an accompaniment to his songs, regularly tuning it or repairing it as needed. Although he treasured greatly his instrument, Tarquin also occasionally used it as a weapon to hit enemies, as a prop to save Dandin from a swamp, and even as a float to save Mariel from drowning.
The Harolina appears in Mariel of Redwall.