Liturgy
Order of worship.
What it means
Liturgy is the ordered form of worship: the fixed sequence of prayers, readings, songs, and actions. For music this is decisive, because a large part of the transmitted vocal music of Europe was written not for the concert hall but for particular places within this order. A distinction is made between unchanging parts, the Ordinary, and changing parts, the Proper, whose texts follow the day of the church year.
Musical use
From the liturgical function follow the length, scoring, and character of many works. An introit accompanies an entrance and adapts to its duration; a Mass setting is organized according to the parts of the Ordinary; a cantata was intended for a particular Sunday and relates to its readings. Whoever performs such music today in a concert detaches it from this context — that is legitimate but changes the perception. Knowledge of the liturgical place helps to understand tempo, weight, and shaping, and explains some peculiarities that otherwise seem arbitrary.
Performance practice
Before a service, clarify the exact order and the place of each piece of music; ask how long actions take, and keep flexible solutions ready — additional stanzas, shortenable sections. Coordinate with those leading the service about signals and transitions. Music has a serving function in the liturgy, and pauses and silence are part of the order. Keep an overview of what is used in the church year, in order to plan sensibly. In concert it is worthwhile to explain the liturgical origin briefly in the programme booklet.