, was added on the next to the lowest line. This, in turn, became our present treble clef,
. In the course of time the signs themselves underwent many changes, until at last from
, 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
one from another, the following individual signs were acquired
. In order to have two distinct values of length, these signs were called longs and shorts, longa