Collectively, influential British folk guitarist Martin Carthy and his daughter, acclaimed fiddler Eliza Carthy, have appeared on more than 200 albums. But somehow 2014’s The Moral of the Elephant is their first as a duo. It was worth the wait. The scribes at AllMusic.com call it a “classic in its field.” And they’re right. Moody and understated, Elephant is an elegantly rendered work that pauses thoughtfully on folk tradition while simultaneously subverting it with gentle grace. Martin and Eliza Carthy perform at the All Souls Interfaith Gathering in Shelburne this Saturday, April 18.