or Cliff, in Music, derived from the Latin word clavis, "a key;" because by it is expressed the fundamental sound in the diatonic scale, which requires a determined succession of tones or semitones, whether major or minor, peculiar to the note from whence we set out, and resulting from its position in the scale. Hence, as it opens a way to this succession, and discovers it, the technical term key is used with great propriety. But clefs rather point out the position of different musical parts in the general system, and the relations which they bear one to another.

A clef, says Rousseau, is a character in music placed at the beginning of a stave, to determine the degree of elevation occupied by that stave in the general clavinary or system, and to point out the names of all the notes which it contains in the line of that clef.

Anciently the letters by which the notes of the gamut were signified were called clefs. Thus the letter A was the clef of the note la, C the clef of ut, E the clef of mi, &c. In proportion as the system was extended, the embarrassment and superfluity of this multitude of clefs were felt.

Gui d'Arezzo, who had invented them, marked a letter or clef at the beginning of each line in the stave; for as yet he had placed no notes in the spaces. In process of time they marked no more than one of the seven clefs at the beginning of one of the lines only; and this was sufficient to fix the position of all the rest, according to their natural order: at last, of these seven lines or clefs they selected four, which were called clefs signatae, or discriminating clefs, because they satisfied themselves with marking one of them upon one of the lines, from which the powers of all the others might be recognized. Presently afterwards they even retrenched one of these four, viz. the gamma, of which they made use to mark the sol below, that is to say, the hypoprolambanomena added to the system of the Greeks.

In reality Kircher affirms, that if we understood the characters in which ancient music was written, and examined minutely the forms of our clefs, we should find that each of them represents the letter a little altered in its form, by which the note was originally named. Thus the clef of sol was originally a G, the clef of ut a C, and the clef of fa an F.

We have then three clefs, one a fifth above the other: the clef of F, or fa, which is the lowest; the clef of ut, or C, which is the fifth above the former; and the clef of sol, or G, which is a fifth above that of ut. These clefs, both as marked by foreigners and in Britain, may be seen in art. 170 of Music; upon which it is necessary to remark, that by a remain of ancient practice, the clef is always placed upon a line, and never in a space. It deserves notice, that the clef of fa is marked in three different manners: one in music which is printed; another in music which is written or engraved; and a third in the full harmony of the chorus.

By adding four lines above the clef of sol, and three lines beneath the clef of fa, which gives both above and below the greatest extent of permanent or established lines, it appears, that the whole scale of notes which can be placed upon the gradations relative to these clefs amounts to 24; that is to say, three octaves and and a fourth from the F, or fa, which is found beneath the first line, to the f, or B, which is found above the last, and all this together forms what we call the general claviray; from whence we may judge, that this compass has, for a long time, constituted the extent of the system. But as at present it is continually acquiring new degrees, as well above as below, the degrees are marked by leger lines, which are added above or below as occasion requires.

Instead of joining all the lines, as has been done by Rousseau in his Dictionary, (plate A, fig. 5.) to mark the relation which one clef bears to another, they separate them five by five; because it is pretty nearly within the degrees to which the compass of ordinary voices extends. This collection of five lines is called a stave; and in these they place a clef, to determine the names of the notes, the positions of semitones, and to show what station the stave occupies in the claviray or general scale.

In whatever manner we take five successive lines in the claviray, we shall find one clef comprehended; nay, sometimes two, in which case one may be retrenched as useless. Custom has even prescribed which of the two should be retrenched, and which retained; it is this likewise which has determined the number of positions assigned to each clef.

If I form a stave of the first five lines in the claviray, beginning from below, I find the clef of fa in the fourth line. This then is one position of the clef, and this position evidently relates to the lowest note; thus likewise it is that of the bass clef.

If I wish to gain a third in ascent, I must add a line above; I must then obliterate one below, otherwise the stave will contain more than five lines. The clef of fa then is found transferred from the fourth to the third, and the clef of ut is likewise found upon the fifth; but as two clefs are useless, they retrench here that of ut. It is evident, that the stave of this clef is a third higher than the former.

By throwing away still one line below to gain another above, we have a third kind of a stave, where the clef of fa will be found upon the second line, and that of ut upon the fourth. Here we leave out the clef of fa, and retain that of ut. We have now gained another third above, and lost it below.

By continuing these alterations from line to line, we pass successively through four different positions of the clef of ut. Having arrived at that of sol, we find it placed upon the second line, and then upon the first. This position includes the five highest lines, and gives the sharpest diapason which the clefs can signify.

The reader may see in Rousseau's Musical Dictionary, Plate A, fig. 5., this succession of clefs from the lowest to the highest; which in all constitutes eight staves, clefs, or different positions of clefs.

Whatever may be the character and genius of any voice or instrument, if its extent above or below does not surpass that of the general claviray, in this number may be found a station and a clef suitable to it; and there are, in reality, clefs determined for all the parts in music. If the extent of a part is very considerable, so that the number of lines necessary to be added above or below may become inconvenient, the clef is then changed in the course of the music. It may be plainly perceived by the figure, what clef it is necessary to choose, for raising or depressing any part, under whatever clef it may be actually placed.

It will likewise appear, that, in order to adjust one clef to another, both must be compared by the general claviray, by means of which we may determine what every note under one of the clefs is with respect to the other. It is by this exercise repeated that we acquire the habit of reading with ease all the parts.

From this manoeuvre it follows, that we may place whatever note we please of the gamut upon any line or space whatever of the stave, since we have the choice of eight different positions, which is equal to the number of notes in the octave. Thus you may mark a whole tune upon the same line, by changing the clef at each gradation. The 7th fig. of the same plate in Rousseau's Musical Dictionary, to which we formerly referred, shows by the series of clefs the order of the notes, re, fa, la, ut, mi, sol, fa, re, rising by thirds, although all placed upon the same line. The fig. following represents upon the order of the same clefs the note ut, which appears to descend by thirds upon all the lines of the stave; and further, which yet, by means of changing the clef, still preserves its union. It is upon such examples as this, that scholars ought to exercise themselves, in order to understand at the first glance the powers of all the clefs, and their simultaneous effect.

There are two of their positions, viz., the clef of sol upon the first line, and that of fa upon the third, which seem daily to fall more and more into disuse. The first of these may seem less necessary, because it produces nothing but a position entirely similar to that of fa upon the fourth line, from which however it differs by two octaves. As to the clef of fa, it is plain, that in removing it entirely from the third line, we shall no longer have any equivalent position, and that the composition of the claviray, which is at present complete, will, by these means become defective.

Thus much for Rousseau's account of clefs. He proceeds to explain their transposition; but as this would render the present article too long and intricate, we refer the curious to his Musical Dictionary, vol. i. page 162. See also Malcom's Dissertation on Music.