In the liturgical practice of the Orthodox Church and Byzantine Rite, a prokeimenon (Greek Προκείμενον, plural prokeimena; sometimes prokimenon/prokimena; lit.
Prokeimena are not selected based on the personal preference of the priest, reader, or choir director.
The basic pattern of a prokeimenon is for the reader to chant a single verse of the psalm or canticle (often announcing the tone as well).
In the Divine Liturgy, the prokeimenon always precedes the Epistle reading, after the singing of the Trisagion.
In Lent and Holy Week, at the Sixth Hour, a prokeimenon is also sung both before and after a reading from the books of Isaiah or Ezekiel.