every note, for the lowest line, being F, the line between that and the C line must stand for A, and the two spaces for G and B; the top line would stand for E, and the space between it and the yellow line for D. Little by little these copyists grew careless about making the lines in yellow, red, and black, and sometimes drew them all in black or red, thereby losing the distinguishing mark of the F and C lines.  In order to remedy this, Guido placed the letters F and C before the lines representing these notes, thus [illustration].  In this way our modern clefs (clavis or key) originated, for the C clef, as it is called, gradually changed its shape to [illustration] and [illustration], and the F clef changed to [illustration], which is our bass clef in a rudimentary form.

Later, still another line was added to the set, thus giving us our modern staff, and another clef, [illustration], was added on the next to the lowest line.  This, in turn, became our present treble clef, [G:].  In the course of time the signs themselves underwent many changes, until at last from [Podium], etc., they became our modern signs.

Before this, however, a grave defect in the notation had to be remedied.  There was as yet no way of designating the length of time a note was to be sustained; something definite in the way of noting rhythm was necessary.  This was accomplished by Franco of Cologne, in the beginning of the thirteenth century.  By disconnecting the parts of the sign [Podium] one from another, the following individual signs were acquired [illustration of Podium broken into three pieces].  In order to have two distinct values of length, these signs were called longs and shorts, longa [illustration], and brevis [illustration], to which was added the brevis in another position [illustration], called semibrevis.  The longa was twice the value of the brevis, and the semibrevis was half the length of the brevis ([L = B B B = S S]).  When notes of equal length were slurred, they were written [illustration].  When two or more notes were to be sung to one syllable in quicker time, the brevi were joined one to the other [illustration], as for instance in the songs of the thirteenth century,

    DIRGE FOR KING RICHARD’S DEATH

    GAUCELM FAIDIT.

    [Illustration]
    [W:  Fortz chose est que tot le maur major dam]

    ROI THIBAUT DE NAVARRE (1250).

    [Illustration]
    [W:  Si li dis sans de laies | Belle diex vous doint bon jour]

or, in modern style,

[G:  g’ a’ b’ c’’ (d’’ c’’) (b’ a’ g’) |
a’ b’ (c’’ b’) (b’ a’ g’) (a’ b’) g’]

In this example we find the first indication of the measuring off of phrases into bars.  As we see, it consisted of a little stroke, which served to show the beginning of a new line, and was not restricted to regularity of any kind except that necessitated by the verse.