ANTIPHON. — From Greek *Ἀντίφωνα* = alternate singing between two choirs. It is a brief formula, composed of one or more phrases that highlights the meaning of the psalm: it is like a key to the interpretation of the psalm itself, from which it is almost always taken, and indicates its main thought, e.g., in the ferial and Sunday offices. Sometimes, moreover, it illustrates the mystery being celebrated, such as the proper antiphons for feasts or the Common of Saints (v.), which are brief prayers, praises, or invocations taken from scriptural passages or composed anew, such as the rhythmic offices very popular in the Middle Ages. Originally, the antiphon was a refrain, a brief intercalary chant in psalms sung by two choirs, which was called an antiphonal psalm. It was repeated at every verse of the psalm; but, in the course of time, both for lack of singers and to shorten the office, it was sung only at the beginning and end of the psalm. In the Mass, however, with the psalm omitted at the Offertory and Communion, only the antiphon remained, and at the Introit the antiphon with the first verse of the psalm.
Properly antiphonal psalmody originated in Antioch (cf. Socrates, *Hist. Eccl.*, 6, 8; Theodoret, *Hist. Eccl.*, 2, 19); it was then introduced into Constantinople by the efforts of John Chrysostom, and into Milan at the initiative of Ambrose, whence it spread to all churches of the Latin rite. In the 6th century the antiphon ceased to be an intercalary chant in the psalms and came to assume the value of what is placed before the psalm, which is said before II. St. Germanus of Paris indeed says: «Antiphona dicta, quia prius ipsa anteponitur» (*Ep. altera de comm. officio*).
Antiphonal singing was already in use among the Jews (Ezra 2:12, 39) and among pagans, as is shown by the Vedic Indians, by the Greeks in the hymn to Apollo of Delphi, and by the Romans in the *versus fascemini*. Tertullian states that the most zealous Christians added to their prayers the Alleluia and to the psalms a concluding formula that those present could repeat (*De Orat.*, 27). Egeria (v.), speaking of the night office in Jerusalem in the 4th century, writes: «Psalmi responduntur», and that one of the priests says a psalm in the morning office «et respondent omnes» (*Peregr.*, 24, 1-9).
In the present Latin liturgy the antiphon is recited in full before and after the psalm at Matins, Lauds, and Vespers on days of double rite; on semidoubles and simples it is begun at the start and said in full at the end of the psalm. In the minor hours of Prime, Terce, Sext, None, and Compline it is always begun at the start and said in full at the end of the three psalms. To intone the antiphon is an honor which, e.g., at Solemn Vespers in cathedral, collegiate, and conventual churches is marked by a pre-intonation made by the first cantor, who, vested in sacred vestments, goes to the place of the one who is to intone.