Partially adapted from Keith Willard's "A Short Shaped-Note Singing History," http://www.fasola.org/introduction/short_history.html:
"Shape note," also known as "shaped-note music," "fa-sol-la," or "Sacred Harp" (in reference to the popular shape note hymnal) is a style of music originated by singing school masters.
Actually, it is both a style of music and a technology.
In shape note music, harmony often depends more on fourths and fifths than on triads, and (interesting) movement in the different vocal lines is more important than a unified sound. For this reason, the sound is often harsh or "primitive." The fourths and fifths also occasionally induce a similarity to the sound of Gregorian chant, in spite of the fact that, at least in the beginning, shape note singers tended to be hard core Protestants.
The heads of the notes are shaped; instead of just the little oval noteheads, we also have rectangles, triangles, and diamonds. The shapes correspond to scale tones. Shaped notes can be divided into two separate systems: four-shape and seven-shape. Both are essentially versions of the Solfege system. It was originated by Little and Smith in 1801.
The four-shape system is currently the most popular. I would hazard that its long endurance is due primarily to the fact that, when you have to come up with seven different shapes, you inevitably have a couple that look awfully similar and are therefore hard to tell apart if you're reading a fast tune. Additionally, there have been a few different seven-shape schemes, whereas the four-shape scheme is pretty well standardized.
The four-shape system is as follows (note: this is for major keys only; see below for minor keys):
scale position syllable shape mnemonic
tonic (1) fa triangle fa is shaped like a flag.
supertonic (2) sol oval sol is round like the sun
mediant (3) la rectangle
subdominant (4) fa triangle (see above)
dominant (5) sol oval (see above)
submediant (6) la rectangle
leading tone (7) mi diamond "Diamonds are for mi."
Obviously, three of the shapes appear twice in any octave. This may seem incredibly problematic, but the singer becomes used to the possible intervals between different shapes (for example: sol going up to la can only be a minor third, a perfect fourth, or a diminished seventh, all of which sound pretty distinct). It sounds crazy but it works.
Minor scales preserve the same interval relationships. A minor scale goes la, mi, fa, sol, la, fa, sol, la.
There are various seven-shape schemes (involving interesting shapes like semicircles and crescents). Laura Ingalls Wilder sang seven-shape.
Some important shape note hymnals are:
- The Sacred Harp (B.F. White,1844)
- Wyeth's Repository (John Wyeth, 1810)
- The Southern Harmony and Musical Companion (William Walker, 1835)
- Missouri Harmony (Allen D. Carden, 1820; supposedly Abraham Lincoln sang from this tunebook)
- Kentucky Harmony (Ananias Davisson, 1816)
- The Hesperian Harp
- The Social Harp (John G. McCurry, 1855)
- The Colored Sacred Harp (Judge Jackson, Ozark, AL, 1934)
- The Easy Instructor(Smith and Little, 1818)
- Harp of Columbia (seven-shape, 1848)
- Harmonia Sacra (seven-shape, Joseph Funk and sons, 1832)
- Christian Harmony (seven-shape; William Walker, 1866)
Try http://www.fasola.org/introduction/note_shapes.html for more information.