It has already been shown how the earlier form of alphabetical notation was gradually superseded by one based on the attempt to represent the relative height and depth of sounds graphically. The alphabetical nomenclature, however, became inextricably associated with the graphic system. The two conceptions rein forced each other; and from the hexachordal scale, endowed with the solmization of ut, re, mi, fa, sol, la—which was a device for identifying notes by their names when talked of, rather than by their positions when seen on a page of music—arose the use of what are now known as accidentals (q.v.).
Of these it may here be said that the flat had originated from the necessity of sinking the B of the scale in order to form a hexachord on the note F in such a way as to cause the semitone to fall in the right place—which in the case of all hexachords was between the third and fourth notes. This softened B was written in a rounded form thus: b (rotundum), while the origi nal B remained square thus : (quadrum). The original con ception of the sharp (q.v.) was to cross or lattice the square B,
by which it was shown that it was neither to be softened nor to remain unchanged. The flat, which originated in the loth cen tury, appears to have been of far earlier date than the sharp, the invention of which has been ascribed to Josquin Des Pres 1521). The B-sharp was called B cancellatum, the cross being formed thus )?'<.
The use of key signatures constructed out of these signs of sharp and flat was of comparatively late introduction. The key signature states at the beginning of a piece of music the sharps and flats which it contains within the scale in which it is written. It is a device to avoid repeating the sign of sharp and flat with every fresh occasion of their occurring. The double bb and the double sharp x are conventions of a much later date, called into existence by the demands of modern music, while the sign of the natural (61) is the outcome of the original B quadration or square B I, (See TONIC SOL-FA and CHEvi notations.)