Skip to 0 minutes and 7 secondsAround 1280, the principal music theorist of mensural notation, Franco of Cologne, describes the notion of perfection. Musical notation is based on a threefold entity of a time unit. Franco of Cologne writes, "This unit is called perfect because it is measured by three tempora." We can keep in mind that the perfect unity consists of three parts.

Skip to 0 minutes and 49 secondsThe rationale of this assumption is based on the theological concept about the status of perfection of the number three. Franco of Cologne points out that the ternary number is the most perfect number because it takes its name from the Holy Trinity, which is true and pure perfection.

Skip to 1 minute and 18 secondsThree tempo units - that is three brevis - yield one perfection. If three brevis make one perfection, what value has a longa?

Skip to 1 minute and 36 secondsActually, it is not possible to give a definitive answer. Learning mensural notation means to face the problem of ambiguity of notational signs. The temporal duration depends on the context. A longa for instance, can assume a value of two or three brevis. There are a couple of rules that help us to know how to read this notation. Those rules are formulated by Franco of Cologne.

Skip to 2 minutes and 16 secondsThe first basic rule says that a longa remains perfect if it is followed by another longa. This rule in Latin is called similis ante similem perfecta. Thus, if there is no further note, we cannot determinate if a longa is perfect of imperfect.

Skip to 2 minutes and 43 secondsA second rule implies that a longa is also perfect if it is followed by two or three brevis.

Skip to 2 minutes and 58 secondsA third rule that Franco mentions describes the concept of imperfection. A longa becomes imperfect or is imperfected by the shorter value of the brevis.

Skip to 3 minutes and 13 secondsIn this example, this happens by a following note: a parte post, as it's expressed in Latin.

Skip to 3 minutes and 22 secondsHere, the same happens by a preceding note: a parte ante in Latin.

Skip to 3 minutes and 32 secondsThe fourth rule defines the relationship between the brevis. If in a frame of two longae there are two brevis, the first longa must be perfect (rule 2).

Skip to 3 minutes and 47 secondsBecause the time laps between the two longae has to fill up a perfectio - a threefold time unit - but there are just two breves, the second will be doubled or altered.

Skip to 4 minutes and 2 secondsFinally, if between the two longae there are three brevis, there will be no alteration.

Skip to 4 minutes and 12 secondsThe perfection and alteration rules by Franco of Cologne you learned in this step represent one essential feature of the mensural notation from the 13th until the 16th century. As we go further, you shall also learn the rules about ligatures that describe the combinations of two or more tones. If you know the perfection and alteration rules as well as the ligature rules, you will be able to read and transcribe mensural notation of the 13th century.

Find yourself between perfection and ambiguity: mensural rules I

Learning mensural notation means to face the problem of ambiguity of notational science: the temporal duration depends on the context. Luckily there are some rules, that can help us.

In this video Prof. Dr. Matteo Nanni and Angelika Moths explain the perfection and alternation rules formulated by Franco of Cologne, which are a central feature of the mensural notation from the 13th to the 16th century.

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This video is from the free online course:

From Ink to Sound: Decoding Musical Manuscripts

University of Basel