original question: Which composition type contains [Mass] as the sub-forms?
answer: sacred music
answer type: Composition type.
auxiliary information: The Mass, a form of sacred musical composition, is a choral composition that sets the invariable portions of the Eucharistic liturgy to music. Most Masses are settings of the liturgy in Latin, the liturgical sacred language of the Catholic Church's Roman liturgy, but there are a significant number written in the languages of non-Catholic countries where vernacular worship has long been the norm. For example, there are many Masses written in English for the Church of England. Musical Masses take their name from the Catholic liturgy called "the Mass" as well. Masses can be a cappella, that is, without an independent accompaniment, or they can be accompanied by instrumental obbligatos up to and including a full orchestra. Many Masses, especially later ones, were never intended to be performed during the celebration of an actual mass.
The composition type [Mass] is contained in what sub-form?