Cantus Firmus - This is when a pre-existing melody is used to underpin a new polyphonic piece. The old melody is often sung as long held notes in one (or more) of the voice parts).

Counterpoint - This is the relationship between two or more independent but interdependent musical lines.

False Relation - This is a striking harmonic feature common in Renaissance sacred music, where two versions of the same note - say, B flat and B natural, are sung at the same time in two different voice parts. 

Homophony - This is rhythmic unison, where all of the voice parts sing the same rhythm at the same time. A good example of homophony is a four-part hymn or chorale.

Isorhythmic - A compositional technique, where the same rhythm is repeatedly used in one or more parts.

Lamentations - These are choral settings of words from The Lamentations (an Old Testament text mourning the destruction of Jerusalem). In a unique feature, the opening Hebrew letter of each verse is often set as one elongated vowel sound, or melisma.

Magnificat - The Canticle (or biblical song) that is sung at the evening service of Vespers. Often referred to as the 'Song of Mary', its text is taken from the account of the Annunciation in Luke's Gospel.

Mass - This refers to the musical setting of the words used at communion services in Christian churches. Typically, this would comprise of the following movements: Kyrie, Gloria, Credo, Sanctus and Benedictus, Agnus Dei.

Motet - Strictly speaking, a motet is a musical piece that sets a biblical text. Most motets are most commonly between 3 and 10 minutes in length, and often have a connection to a particular feast in the church year.

Polyphony - This is when several voices sing independent but interdependent musical lines at the same time.