The Propers for the Mass for Pentecost include the beautiful Sequence Veni Sancte Spiritus (chant and translation below). Sequences, once a regular part of the Church’s liturgies, now occur infrequently, being obligatory only twice a year: on Easter and Pentecost Sundays.
Sequences are generally believed to have originated as an elongation of the melismatic chant Alleluia, perhaps out of particular devotion, perhaps for more practical reasons such as accompanying an extended Gospel procession. That Sequences are sung after the Alleluias from which they developed is well-established; even the name Sequence (Sequentia) comes from the Latin ‘to follow’.
Much like the double Alleluias during Eastertide, the Sequence can cause looks of confusion to be directed towards the organ loft since the [post Vatican II] Roman Missal gives the order Sequence - Gospel Acclamation, whereas the Graduale Romanum (from which the Choir sings) stipulates Alleluia - Sequence.
To understand why two key books give conflicting instructions is to appreciate that the Gospel Acclamation and Gregorian Alleluia are, in fact, two distinct entities, the former being brief with a text related to the Gospel of the day, the latter a longer meditation usually taking a verse from one of the psalms.
When the Gregorian Alleluia is replaced by the Gospel Acclamation, the Sequence precedes it. At Masses where the Gregorian Alleluia is sung, it is followed by the Sequence. The repetition of the Alleluia after its verse is omitted and the Sequence sung immediately. The Amen. Alleluia. ending provides the conclusion to the invocations of the Sequence and the Alleluia repetition omitted earlier.
Sequences are a beautiful embellishment of the liturgy, one made rather poignant given the infrequency with which they now occur.
Holy Spirit, Lord of light,
From the clear celestial height
Thy pure beaming radiance give.
Come, thou Father of the poor,
Come with treasures which endure;
Come, thou light of all that live!
Thou, of all consolers best,
Thou, the soul’s delightful guest,
Dost refreshing peace bestow.
Thou in toil art comfort sweet;
Pleasant coolness in the heat;
Solace in the midst of woe.
Light immortal, light divine,
Visit thou these hearts of thine,
And our inmost being fill:
If thou take thy grace away,
Nothing pure in man will stay;
All his good is turned to ill.
Heal our wounds, our strength renew;
On our dryness pour thy dew;
Wash the stains of guilt away.
Bend the stubborn heart and will;
Melt the frozen, warm the chill;
Guide the steps that go astray.
Thou, on us who evermore
Thee confess and thee adore,
Thy sevenfold gifts descend:
Give us comfort when we die,
Give us life with thee on high;
Give us joys that never end. Amen. Alleluia.