34. Time and its Notation.—That the early Plain-Song had a general rhythm, often approaching regularity, was a matter of course, since all prose has some rhythm. But strict rhythm was for Gregorian melodies incidental and even objectionable. Music, however, could not avoid being affected by the rhythms and metres of poetry, in which accent and time-values were systematized. The most plausible theory of the appearance of a time-system in music is that which attributes it to certain verse-schemes that were adopted as patterns for musical phrases.
The first clear reference that we have to this subject (13th century) assumes the existence of equal measures, implying a sense of strict rhythm. It presents the notion that triple rhythm is better than duple, and in the subdivision of the parts, a long note is assumed to be equal to three shorter ones unless the contrary is specified—all different from our present view. With these fundamental conceptions of time, what was called Mensural or Measured Music rapidly developed into numerous metric patterns.
Tempus perfectum was the term for triple rhythm and tempus imperfectum
for duple, while prolatio major indicated a triple division of long
notes and prolatio minor a duple division. This exaltation of triple types
may have been due to various causes—it was often associated with the
theological doctrine of the Trinity!
Immediately arose the need for a notation corresponding
to these ideas. The old neumes were still used and also the
square characters derived from them. The virga, [Symbol]*, and the
punctum, [Symbol]*, had passed into the longa, [Symbol]*, and the brevis, [Symbol]*.
The former now came to be the standard long note, the latter
the standard short note. One longa in major prolation was
equal to three breves, in minor prolation to two. The system
of notes was further increased by the maxima, [Symbol]* (double longa)
and the semibrevis, [Symbol]* (half-brevis), and after 1300 by further
notes of less value—the minima, [Symbol]*, semiminima, [Symbol]*, and finally
the fusa, [Symbol]*, and semifusa, [Symbol]*.
These notes were written at first as above, with solid or black heads.
In the 15th century open or white heads appear, and in the 16th they
begin to be rounded. The derivation of the modern forms is evident:—*
