ACCIDENTALS. In spite of the strict laws gov erning plain chant and the use of the old Church modes, the human ear from the earliest times felt the need of a 'leading tone.' The tone of the scale that was subject to this modification was B. Thus at a very early time this letter was written in round (b) and later square (6) form to indi cate whether the lower or higher tone was to he sung. It is easy to see how from these two forms arose our fiat and natural ). Toward the end of the thirteenth century the sign 6 was care lessly written S. and being applied to other tones than B. denoted the higher of the tones on the same degree. Thus, Ft: denoted the modern but Fb was the same as our b' natural, just as Bb was regarded as the natural tone and 11:`,. (our 13) a chromatic alteration of Bb. As a key signature the sign 0 appears first in the Church modes, but denoted only a transposition of the original mode. MOPES.) Even in the tepfith century a 0 was used as a sigu of resolu tion for a note having a r. or El these two signs
were idyll/neat) ; and vice versa a or El served to resolve a b. The signs of the double sharp and double that I X, 1/b) cannot he traced further back than the beginning of the eighteenth cen tury. the sign X arose from writing the older .1: in this positionC, Before the beginning of the ent.voth century accidental sharps, fiats, or signs of resolution appeared very seldom in The singer was supposed to introduce the necessary chromatic alterations during the actual performance. As lung as the Church modes reigned supreme no use was made of regu lar key-signatures. A flat or sharp placed at the beginning of a piece denoted only transposi tion. But as soon as the modern major and minor scales displaced the modes the necessity of key-signatures arose. in order to avoid the great number of accidentals.