Clausula
Medieval closing formula or organum section.
What it means
Clausula has two meanings in music history, which must be kept apart. On the one hand, the word designates a closing formula in which the voices converge on the final note in a fixed manner; in German, “Klausel” is used for this, which has its own entry in the glossary. On the other hand, it designates a particular section of early polyphony.
Musical use
As a section of the polyphonic music of the late twelfth and early thirteenth centuries, the clausula is part of an organum in which the underlying liturgical melody is led in the lower voice in a particular rhythmic pattern, while the upper voice, likewise rhythmically bound, runs above it. Such sections were collected, exchanged, and inserted into different organa. The motet developed from them: a text of its own was underlaid to the upper voice of a clausula, and a new genre arose from this.
As a closing formula, the clausula describes the way in which closes are formed in modal writing. Not chord progressions are at the centre but the movement of individual voices: one voice reaches the final note stepwise from above, another from below, often with a semitone obtained through musica ficta. The various voice formulas were named after the voice in which they typically lie.
The later cadence of major–minor tonality emerged from these voice formulas; it can be understood as their harmonic summary.
In the circle of the Notre Dame school around 1200, clausulae were composed separately and inserted as interchangeable sections into organa. Over a tenor of a few chant notes, often repeated in rhythmic patterns, one or more upper voices moved in discant style. The motet emerged from these sections when texts of their own were underlaid to the upper voices.
Performance practice
When you sing music of this period, watch at closes the movement of your own voice to the final note — it follows a formula, and the other voices expect it. Settle in the ensemble which final notes are raised. And treat rhythmically bound sections with an even pulse instead of phrasing them freely.