The General Instruction of the Roman Missal notes that there are many times when silence is to be part of the ritual. Among these is a silence after each of the first two readings and a silence after the homily. It is needed when the scripture has been proclaimed and listened to well. There is something to reflect on, an appreciation for a quiet moment to turn it over or to let one word or phrase echo in one's mind. It is silence together - for all the ministers and everyone in the assembly. No on is busy getting music or books or papers ready or seating latecomers. When the length of the silence is the same week after week, there is no nervous wondering when it will end. It becomes a habit.
The responsorial psalm grows out of this silence. The style of the music both continues the reflection and draws in the active participation of the assembly. Often the proper psalm refrain becomes a mantra carrying the Sunday scriptures through the week in the hearts of the faithful. Following the practice of the Jewish synagogue, the community traditionally replies to a scriptural reading by singing a psalm or biblical canticle. Today it is called the responsorial psalm, a designation expressing the structural nature of the text and the manner in which it is used as a response to the proclaimed Word of God.
Although some call attention to the meditative quality of the psalm, reflection is not its primary function. Rather, the psalm serves as the people's response to the reading just proclaimed. The scriptural message is to reverberate in the assembly whose members together acknowledge and respond to the word of God by using the word of God. The selection of the responsorial psalms found in the Lectionary was done with the utmost care.
The Order of Mass considers it normative that the responsorial psalm be sung. The reason is threefold: the genre of the psalms as lyrical compositions calls for singing; the psalm is a response to the spoken word and ritual structure does not customarily respond to speech with more speech; this is the only time in the liturgy when a psalm is used for its own sake and not to accompany a ritual action. Every effort, therefore, is to be made to sing the psalm response.
The person leading the assembly in the singing of the responsorial psalm is referred to as the cantor or the psalmist. The psalm should be sung at the ambo, since the psalm is part of the Word of God and the ambo is the place from which that Word is proclaimed. The responsorial psalm is the assembly's acclamation of the proclamation of God's Word in our midst. That is how we worship: proclamation followed by acclamation.
[Source: Bulletin of April 11, 2010, St. Paul's Cathedral Parish, Saskatoon, Saskatchewan, Canada.]