It's a form of 4-part choral singing that developed in America in the 17th and 18th centuries. It has survived primarily in the south. No accompanying instruments are used. Over the last few decades, this style of singing has become popular among many people in the north. Among those who sing this stuff today, the northern folkies probably outnumber the active southerners, but the southerners are still way better at it. The songs are mainly old, old hymns, but the singers, especially in the north, aren't necessarily interested in the words. What's really nifty are the archaic harmonies that make the hairs stand up on the back of yr neck. The most commonly used songbook is entitled, "The Sacred Harp," a reference to the human voice. For more info go to http://www.fasola.org