Lining out is a musical technique in which one individual reads or sings a line of a song slightly ahead of other members of a choir or congregation, allowing them to follow. It is especially common in European and American religious music, especially in a-cappella singing. The version of the line sung by the leader may not always be exactly the same as the version of the line sung by the main group.
The exact origin of lining out is unknown, but it certainly existed by the 17th century, when the Church of England approved it as a method of hymn-singing. Many churches did not have a sufficient number of psalters for every member of the congregation to have a copy of the hymn. Literacy was also less common in the 17th century than today, meaning that even if they had copies of the hymns, some members of the congregation would have been unable to read them. As a result, a leader, called a precentor or clerk, would chant the line of the song before the congregation sung it.
Strange though it may seem, lining out was the source of some controversy in the 18th century. Some writers complained that its mixing of different tempos and melodies, with each singer embellishing the song individually, produced an unpleasant cacophony. Others condemned "regular singing" -- singing using notes printed in a book -- as a radical innovation and even a pop-type element of religious ritual, offensive to Puritan sentiments.
Increased access to printed songbooks and spreading literacy decreased the popularity of lining from the 18th century onward, but it continued to exist in some congregations. In some cases, this was motivated by a lack of access to hymnals or literacy, but in others lining out had become part of a rich tradition of sacred music, valued in its own right. In the United States, some predominantly African-American churches maintained a tradition of lining out, as did many Primitive Baptist and Regular Baptist congregations. In the United Kingdom, lining out survived in Scotland, particularly in Gaelic-speaking churches on the Isle of Lewis.
Some congregations combine lining out with more traditional hymnody. The clerk or precentor may line out the first verse of the hymn, but then instruct the congregation to "sing on." In these cases, the form of lining out is maintained for primarily traditional reasons and the majority of the congregation do not actually need it.