Other ways in which shape-note music is an "alternative choral music":
Lack of a concept of blend. People who hear shape-note singing for the first time probably react first to the raucous sound, when compared to "classical" choral singing. Some shape-note singers indeed sing very loudly, but it is a misconception to think of the difference just as more volume. The timbre of a shape-note singing group is more complex because it is deliberately unblended. Individual voices can often be heard in the mix, in part because each voice has its own signature of upper partials.
Again making a comparison with the organ, it is a bit like drawing all of the 8' stops at the same time, so that principals, flutes, and reeds all sound together. The result is loud, but not in the same way that a plenum of 8', 4', and 2' principals is loud. Rather, the loudness comes from the simultaneous sounding of different timbres that do not blend together into a single whole. (The tradeoff is less clarity of sound than the usual practice of using a single collection of 8', 4', and 2' stops, plus mixtures.)
Here is what the hymn tune ST. THOMAS (found in The Sacred Harp but also in most mainline hymnals) sounds like with this treatment. I am playing it on a Rodgers digital organ with the following registration:
- Great: Principal 8, Trompette 8, Rohrflöte 8
- Choir: Spitzgeigen 8, Holzgedeckt 8, Cromorne 8
- Swell: Geigen Principal 8, Bourdon 8, Hautbois 8, Trompette 8
- Pedal: Principal 8, Gedeckt 8, Trompette 8
- Choir to Great, Swell to Great, Great to Pedal
How do you decide what pitch to start at? The culture of Western art music has gradually evolved a practice in which pitches notated on paper are supposed to correspond to specific physical pitches. Though there is disagreement on exactly what the reference pitch is, setting the pitch A4 to 440 cycles per second is widely adopted in the United States.
In shape-note music, there is no external reference pitch, and each song is pitched according to the needs of the moment (how high the song is notated, what kinds of singers are present, what time of day it is, and so forth). In theory, a cappella choral singing can also adopt this attitude toward pitch, but in practice I have found that choral directors almost always tune their choirs to a tuning fork or a keyboard. If singers struggle with a certain choral work, why not just stop, say "Let's start again with C a little higher," sound the note, and give it a try? First make sure that none of your singers have perfect pitch, though!