In Catholic and other Western Christian traditions, a responsorial psalm is an exchange between a cantor who sings a psalm and a choir or congregation that replies at pre-established intervals with a refrain. This is a powerful oratorical tool which involves all present in the recitation of liturgy.
The most usual method of performing a responsorial psalm is for the cantor or priest to sing a verse and then for the choir or congregation to answer with the refrain, but there are alternate methods of recitation. These include group choral singing wherein varied elements of the choir deliver the verses and refrains, or choral recitation of the verses and singular proclamations of the refrain.
The responsorial tradition has its roots in the cantus responsorius, an antique Christian tradition begun as a liturgical element. With the fading of High Church traditions and the institution of non-Latin mass the responsorial psalm has lost these connective elements but remains a common fixture in Christian ceremonies of diverse sects.
The traditional High Latin Mass of the Roman Catholic Church contains two prescribed responsorial psalms. These are the Alleluia and the Offertory, the latter of which has largely fallen out of fashion while the former retained a significant degree of usage at the dawn of the 21st century.