72. But it is obvious, that the lower part of the scale could not be written on this clef. Another, therefore, is used, marked thus o:, which is called the F clef, or bhss clef. It is placed on the fourth line of the staff, and signifies that the F next below middle C is written on the 4th line. In this clef the lower part of the scale is written thus— Music for bass volces and instruments, such as the basso, violoncello, bassoon, and the left hand part for keyed in struments, is written on this clef. Middle C, it may be ob served, is on the first ledger line above the staff in the F clef, and the same C is on the first ledger line below the staff in the G clef; so that the highest line of the bass clef cor responds Avith the second ledger line below the treble ; and the G, A, and B, here written on the 4111 space, the 5th line, and above the staff, are the same notes Avhich, in the G clef, are written by means of ledger-lines below the staff. This circumstance malAes it extremely convenient to use these two clefs together for the rig-ht and left hand parts of keyed in struments. The F clef is sometimes placed on the third line instead of the fourth, in old music; but this practice is now obsolete, except in music for the church.
73. Though these two clefs comprehend the whole extent of musical sounds, yet the parts for instmments and voices which are called tenor and counter-tenor, whose compass comprehends the upper part of the bass and lower part of the treble, could not conveniently be written on either gi of them. A third clef is therefore used, marked thus which represents the letter C, meaning the middle C of the scale of the piano-ft,rte. This is placed on the fourth In Italy and Germany, no other clef is generally used for the riEdtt hand part of keyed instruments. In this country, many performers on keyed instruments are disposed to be contented with the knowledge of the G and F clefs ; but the student who would peruse the works of the great foreign masters, must not yield to such indolence.
74. In music for keyed instiuments, a staff being wanted for each hand, they- are joined together by a brace, thus— the upper part for the right hand, and the lower for the left : and in the same manner music for different voices and instru ments is frequently written, which is called a score. The score brings the whole composition under the eye, and thus furnishes the most profitable lessons to the student. Let us itow attend somets hat particularly to the intervals in the scale.
7.5. The word interval, means the difference in respect of pitch between two musical sounds. Thus, the first degree of the scale, from C to D, is the interval of a tone; from C to E, it is plain, is a greater difference in respect of pitch, or a greater interval; from C to F is an intert al still greater, and so on. Intervals are named according to the number of sounds in the diatonic scale of which they consist, including both the lowest and highest sounds; and the reckoning is almost always from the lowest note upwards. The intervals so reckoned are denoted by corresponding figures. Thus, the interval from C to D is a second, and is denoted by the figure 2. The interval CE is a third, figured 3, because three sounds are to be named in reckoning it, viz. CDE5 and if the two notes CE be sounded together, the resulting compound sound is called a third, although the intermediate sound D be omitted. So also CE is a fourth, CG a. fifth,
CA a sixth, CB a seventh, and Cc an eighth or octave, as before observed; denoted by the figures 4, 5, 6, 7, S ; and these intervals are so named, whether any of the interme diate sounds be heard at the same time or no. The interval from C to d (the second note in the octave above) is a ninth, figured 9. But it is to be observed, that musicians use the names and figures second, third, fourth, &c. even when the intervals are enlarged by octave, or by two or more octaves. Thus, the above interval C d is called also a second, and figured 2. C c is called a third, C f a fourth, C g a fifth, &c. Musicians seldom speak of tenths, elevenths, twelfths, &c. and still seldomer figure them, but as 3ds, 4ths, 5ths, &c. Intervals enlarged by one or more octaves, are sometimes called compound intervals.
76. It is necessary to attend particularly to the number of tones and semitones of which these intervals respectively consist. And here we nmst observe, that the semitone is reckoned, as the name implies, one-half of the tone, and, consequently, two semitones equal to a tone. This, as WC shall afterwards learn, is by no means accurate; but it is sufficient for our present purpose.
The second,.CD, is one tone; the third, CE, includes the intervals of two tones ; the fourth, CF, consists of the intervals of two tones and one setnitone; the fifth, CG, is one tone larger than the fourth, or it includes three tones and one semitone; the sixth is one tone larger, that is, it in cludes four tones and one semitone; the seventh, one tone more than the sixth, includes five tones and one semitone; lastly, the octave, one semitone larger, consists of five tones and two semitones.
77. But if we reckon seconds, thirds, fourths, &c. succes sively, from the other six notes of the scale, we shall find that the intervals of these names do not always consist of the same number of tones and semitones with these which we have just reckoned from C. Thus, counting from D, the second DE is a tone like that reckoned front C. But the third DE consists only of a tone and a semitone; whereas the third, counted from C, consists of two tones; and there is a very striking difference in the effect of these thirds. A third, consisting of two tones, is called a major third; and one consisting of a tone, and a semitone, a minor third. The fourth, reckoned from D, is of the same kind with that counted front C; for though the degrees of tone and semi tone clo not occur in the same order when we count from D to G, as when we count from C to F, yet we find the same number, namely, two tones and one semitone. The relation, therefore, of the two extreme sounds, D and G, is exactly the same as that of C and F. In the same manner, we find the fifth DA, and the sixth DB, to be of the same kind with those intervals counted from C. But the seventh DC con sists of four tones and two semitones, or, calling the two semitones one tone, of five tones. It is, therefore, a tone less than the seventh CB; which consists of five tones and a semitone. This last, then, is called a major seventh, and the other, DC, a minor seventh.