The purpose of the responsorial psalm and Alleluia
Someone asked me, why we sing the Psalm and Alleluia in between the Readings. We Catholics are accustomed to hearing the Responsorial Psalm and the Gospel Acclamation sung or recited between the Readings. These were instituted by the Second Vatican Council, in order to foster the meditation on the Word of God.
Following the first reading, we raise our mind and heart reciting or singing the Responsorial Psalm taken from the Book of Psalms in the Old Testament. Since the early centuries of the Church, what was known as the Graduale and the Sequence were sung between the readings. According to the General Instruction of the Roman Missal, the Responsorial Psalm forms an integral part of the Liturgy of the Word and the Psalm should correspond to the first Reading (cf. GIRM #61). In fact, it has a thematic relationship to the first Reading and it is people’s response to God’s Word. In the current lectionary, the Responsorial Psalm comes with antiphon which enables the assembly to sing after every verse sung by the cantor.
There is also an option of using seasonal Psalm, namely, a psalm that fits with the mood of the Church Season. This allows the assembly to reflect on the meaning of that season.
Gospel Acclamation/ Alleluia:
The Gospel Acclamation is a song of praise, with a verse from the Gospel. Except during the season of Lent, we sing “Alleluia”. It is usually sung by everybody, standing and is led by the cantor. The verse is sung by the cantor. We stand while singing this song of praise because this posture would help the assembly to welcome and greet The Lord, who is going to speak to us in the Gospel.