Antiphon (music)

In Christian liturgy, an antiphon is the name of a short section, between the cleric, and usually the crowd. These sections are either spoken (the priest asks something, and the crowd gives a predefined answer, also spoken), or they are sung. When they are sung, the often use simple melodies. Antiphons are very old: In the 4th century they were used in what is called Ambrosian chant today. In liturgy, antiphons are not used on their own: the priest or person of the clergy says or chants these, while performing a ritual. In many pieces of church music, the choir (who replaces the crowd) starts singing as a response to an antiphon. 
In more modern forms of church music (such as Gospels, but also traditional African music), there's a tradition of call and response. A lead singer calls something, and the choir responds.