The components of Vespers:
On Sundays, Feasts, and Commemorations the principal vespers falls on the even, as the beginning of the observance. On ferias vespers falls on the day.
-opening versicles
-psalms with antiphons
-chapter
-responsory
-hymn
-versicle
-Magnificat with antiphon
-preces
-versicle: Dominus vobiscum
-prayer
-versicle: Dominus vobiscum
-versicle: Benedicamus Domino

-memorial(s), each containing:
—antiphon
—versicle
—prayer

-versicle: Dominus vobiscum
-versicle: Benedicamus Domino

General notes
–Canonical vespers is generally sung throughout, in the chancel, typically around 4 p.m.
–On Good Friday it is said privately in alternation in the chancel.

Notes on the components of vespers:
-Opening versicles
—The final portion, ‘Alleluya’ is replaced with ‘Laus tibi Domine, Rex eterne glorie’ from Septuagesima to Easter.
–On Maundy Thursday, the Vigil of Easter and the Vigil of Pentecost Vespers is united with the conclusion of the Mass; there are no opening versicles.
–On Maundy Thursday, Good Friday, and Holy Saturday there are no versicles.
–On Easter Day and during the week, Kyrieleyson (Lux et origo) replaces the opening versicles

-Psalms and antiphons:
—the psalms are taken from 109 through 147 in order, omitting certain psalms that are sung at other times): Sunday 109-113; Monday 114-116, 119-120; Tuesday 121-125; Wednesday 126-130; Thursday 131-132, 134-136; Friday 137-141; Saturday 143-147.
–On the Vigil of Easter there is only one Psalm: 116.
–On Easter Sunday and through the octave there are only three psalms: 109-111.
—each of the ‘psalms’ is concluded with ‘Gloria Patri’–except on Thursday, Friday and Saturday of Holy Week, on All Souls Day, and on Vigils of the Dead.
—the final antiphon is concluded with a neuma, except from Passion Sunday until the Octave of Easter and in the Office of the Dead, and on All Souls’ Day.
–throughout Eastertide there is only one antiphon on the psalms.

—When several Sundays take their matins readings from the same Lection (i.e. Book of the Bible), then on subsequent Sundays with such a group only the first antiphon is sung, together with all five psalms; however, on the final Sunday before Septuagesima and before Advent, all five antiphons are sung.
—during Eastertide, only one antiphon on the psalms on ferias and on some feasts.
—on commemorations, only one antiphon on the psalms

-Chapter
–There is no chapter on Maundy Thursday or Good Friday or the Easter Vigil.

-Responsory
–A responsory is sung at first vespers on higher rank feasts and Sunday
–When the first Sunday of a ‘History’ has been deferred, the responsory will still be sung unless a memorial of the Sunday has been made where it ‘should’ have been begun.

-Hymn
–The hymn is omitted from Maundy Thursday through octave of Easter; instead, the Gradual and Alleluya are repeated from the mass of the day.

-Versicle
–there is no versicle on Maundy Thursday or Good Friday or the Easter Vigil.
—a simpler versicle tone is used throughout the octave of Easter, Vigils of the Dead, and All Souls’ Day. In these cases the response is sung.

-Magnificat and antiphon
—the antiphon is concluded with a neuma, except from Passion Sunday until the Octave of Easter and in the Office of the Dead, and on All Souls’ Day. On certain feasts the antiphon is sung through entirely both before and after the canticle.

-Preces
—said only on ferias, except not when during the Advent Ember Days there is a reading from the Gospel at Matins.
—during quadragesima an additional. ‘penitential’ psalm, 129, is said.
–On Good Friday in place of the preces Pater noster and Ave Maria are said privately, along with Ps. 50.
—omitted at the Said Office of the Virgin

-Versicle before the prayer
–omitted on Good Friday

-Prayer
–On Maundy Thursday and the Easter Vigil this prayer is the Post-communion of the Mass.

-Versicle and Benedicamus Domino
—the melody for Benedicamus Domino is selected based on the dignity of the feast or feria
–omitted on Good Friday.
—omitted at the Said Office of the Virgin
–On Holy Saturday the text is ‘Ite missa est’.

-Memorial(s)

-Versicles after the memorials
—omitted if there are no memorials
—the melody for Benedicamus Domino is the ordinary one

Processions after Vespers normally function as extended memorials.