CDEFGA BC DEFGABC These notes correspond with the white keys of the pianoforte or the diatonic scale when C is key-note, no allowance being made for the black keys, which, as we have seen, divide the tones into semitones. Those semitones which do not occur with C as key-note are represented by the signs t,' (sharp) and [2 (flat). The sign ,t-7, prefixed to a. note, elevates it a semitone in the scale, raising, for example, F to F sharp. p lowers the note by a semitone, depressing B to B fiat. When a note which has been elevated by a sharp, or depressed by a flat, is to be restored to its original place, the character I; (natu ral) is prefixed to it.
The names of the intervals correspond to the degrees of the staff, but it has been seen that intervals of the same name are not necessarily equal. If the sign of a fiat or a sharp be prefixed t-? either note of an interval, it still preserves its name of a third, a fifth, etc.; but to distinguish intervals of the same degree, the qualifying epithets of major and minor, augm.:,:ited and diminished, are used.
The different keys in music are best understood by reverting to the scale of triads, on which the diatonic scale is founded Taking a series of triads, of which the dominant of each is the key-note of the next, we obtain the foliewinP:scale, extended both upwards and downwards from C: (517 Ely a Bi, Dfx F 2.112 C 42 G Bb- DI' A a E a B n F: A Qt. k G5 D D: F.: A: 6: ES 6: • Key of C: . • Key as G, one sharp Key of F, one flat : • • Key of two flats Key of D, two sharps Key of Et, three flats Key of A, three slurps * ' Key of AL, four data Key of E, four sharps Key of Db., five Sots Key of B, fire sharps
Key of GI, xis flats Key of F:, six sharps Each triad is composed of the key-note, its mediant, and dominant, and the scale of ea hi key is composed of the triad of the key-note, with the triad immediately preceding and that immediately following it. Each key is succeeded by the key of its dominant, and if we begin with the key of 0 (in the middle of the scale), each key acquires an addi tional sharp until we reach the key of F with six sharps. These are the sharp keys. If, beginning again with the key of C, we go back instead of forwards in the scale of triads, we obtain the flat keys; each key has an additional flat to that above it, till we come down to the key of Gy with six flats. This key in instruments with temperament is exactly the same with that of F:',..', and on this account it is not generally found conve nient to extend the keys beyond six, or at most seven, sharps or flats. CI: with seven sharps is the same as li)-, with five flats, and C12 with seven flats is the same as B with five sharps. In music written in these keys, double sharps and double flats occur, which are indicated by the characters X and IX, respectively. In writing music in any key with sharps or fiats, it is usual, instead of prefixing the sharp or flat to each note when required, to place the sharps and fiats belonging to the key together after the clef, on the legree to which they belong, and such collections of sharps or flats are called the signa nature.