BobKnight: short answer: hymn singing from an American 18th-early 19th century tradition. The music is written with various (4 or 7) shapes for the note-heads which indicate the place of the note in the scale (in addition to the usual staff lines). The most commonly used text/system is called the "Sacred Harp". For more, see www.fasola.org, also Warren Steel's site.

~ Becky in Long Beach