What is "shape note"

n. a system of music notation designed to facilitate choral singing

Shape notes are a music notation designed to facilitate congregational and community singing. The notation, introduced in 1801, became a popular teaching device in American singing schools. Shapes were added to the note heads in written music to help singers find pitches within major and minor scales without the use of more complex information found in key signatures on the staff.

Shape notes of various kinds have been used for over two centuries in a variety of music traditions, mostly sacred but also secular, originating in New England, practiced primarily in the Southern region of the United States for many years, and now experiencing a renaissance in other locations as well.