Mensural Notation

a system of representing musical sounds that was used from the 13th to the 16th century.

Unlike the earlier, plainsong notation, mensural notation made it possible not only to fix the pitch but also to mark the relative duration of sounds. In the 13th century, the following signs were employed to indicate duration, values (in order of diminishing duration): maxima or duplex longa (largest or double long), longa(long) brevis (short), and semibrevis (half as short). In the 14th century still smaller duration values were introduced: minima (smallest) and semiminima. There were special signs to indicate rests.

Initially, the basic unit of duration was the longa; later the brevis, and still later, in the 14th century, the semibrevis became the basic unit. The maxima and minima were always divisible into two notes of a lower value, whereas the remaining notes could be divided into two and three notes. The types of rhythmic divisions were called mensura; they were indicated by special signs placed at the beginning of a line. Later, for the purpose of indicating long durations, white notation was introduced; the semiminima and the still smaller duration values that appeared later, ihefusa and semifusa, were indicated by both white and black notation. The system of mensural notation, which reached its final stage of development in the 16th century, was the basis of modern notation.