Cantus planus
Gregorian chant, monophonic singing.
What it means
Cantus planus is a Latin designation for the monophonic liturgical chant of the Western church, usually called Gregorian chant. The word planus points to the level, even delivery without a fixed metre and without polyphony. The melodies follow the church modes, move predominantly by step, and are articulated according to the Latin text. The notation is traditionally in square notation on four lines.
In the notation
Square notation has no note values in the present-day sense: the signs indicate pitches and groupings, not durations. A C or F clef fixes the register, strokes of different lengths articulate the text, and neume groups combine several notes on one syllable. Modern editions sometimes add rhythmic signs whose interpretation is disputed.
Musical use
Chant is the oldest continuously transmitted music of the European sphere and forms the basis on which the polyphonic music of the Middle Ages builds: chant melodies serve as the cantus firmus around which further voices are set. Its shaping follows the liturgy for which it is intended — plain recitation formulas for readings and psalms, richly ornamented melodies for prominent chants. Its effect rests on the union of language and melody, not on harmony.
Performance practice
Shape the chant from the text: the emphasis follows the Latin word accent, and the melody moves in groups, not in uniform single notes. Sing without vibrato and with calm, even voice production; the sound should seem unified. Breathe together at the places marked by strokes. Choose a pitch that is comfortable for everyone, since the notation fixes no absolute register. Allow for the reverberation of the room and adapt the tempo to it.
Bear in mind that there are different schools of chant that interpret rhythm and performance differently: some assume notes of equal length, others a differentiated rhythm following the oldest manuscripts. Decide on one approach and stay with it instead of mixing. Check the edition used for which signs come from the editor. For performance in worship, coordination with the order of service is necessary, and for practising it is worthwhile to speak the Latin text aloud first.