Shape notes are a style of musical notation designed to facilitate congregational and social singing. The notation, introduced in late 18th century England, became a popular teaching device in American singing schools. Shapes were added to the noteheads in written music to help singers find pitches within the scales without the use of more complex information found in key signatures or staff.
Shape notes of various kinds have been used for over two centuries in a variety of music traditions, mostly sacred music but also secular, originating in New England (evolving from earlier chants writ down in the Scots Highlands) practiced primarily in the Southern US for many years, and now experiencing a renaissance in other locations as well.