and
, which are sometimes erroneously referred to as being the initial letter of our word common (as used in the expression "common time"). The transition from the older style of measure-signature to the present one seems to have occurred during the century following the invention of opera, i.e., from about 1600 to about 1700 A.D.
The rest came into use very soon after "measured music" began to be composed and we soon find rests corresponding with the various denominations of notes in use, viz.:
The terms applied to these rests vary in different authorities, but it will be noted that the pausa, semi-pausa, and suspirum correspond respectively to the double-whole-rest, whole-rest, and half-rest in use at present.
The bar and double bar may be developments of the maxima rest (as some writers suggest) but are probably also derived from the practice of drawing a line vertically through the various parts of a score to show which notes belonged together, thus facilitating score reading. The bar may occasionally be found as early as 1500, but was not employed universally until 1650 or later.
The number of lines used in the staff has varied greatly since the time of Guido, there having been all the way from four to fifteen at various times and in various places, (four being the standard number for a long time). These lines (when there were quite a number in the staff) were often divided into groups of four by red lines, which were not themselves used for notes. These red lines were gradually omitted and the staff divided into sections by a space, as in modern usage. The number of lines in each section was changed to five (in some cases six) for the sake of having a larger available range in each section.
The clefs at the beginning of the staffs are of course simply altered forms of the letters F, C, and G, which were written at first by Guido and others to make the old neume notation more definite.
The staccato sign seems not to have appeared until about the time of Bach, the legato sign being also invented at about the same time. The fermata was first used in imitative part-writing to show where each part was to stop, but with the development of harmonic writing the present practice was inaugurated. Leger lines came into use in the seventeenth century.