When the dominant chord is to make a cadence on the chord of the key, its third ought not to be doubled, because as that third niust rise to the key-note, two parts wottld then be obliged to move in octaves or unisons.
In compositions of fewer parts than four, the octave or fifth are to be omitted rather than the third, because this determines the species of the chord as major or minor.
110. Common chords succeed each other most ag,recably, when the two chords IlitVC one or more sounds common to both ; and this w ill be the case when the bass rises or falls by a fourth or by a third, as in the following examples: These two different forms of each position make the dis tinction between close and dispersed harmony. Vet on comparing them, the student will find that the effect of the uppermost sound is so decided, that there is as much propriety in calling the two forms of each the same posi tion, as there is in calling them all the common chord, because the fundamental bass remains. And this remarkable effect of the bass and highest part is always observable; therefore. the right ordering of these two parts is to be most carefully attended to. They are called the extrenze parts, and the others are called the midd/e parts, or inner parts.
The position in which the octave is the highest sound, is the most satisfactory of the three; and hence this position is g,enerally preferred at the close of a strain or piece of music. That in which the third is highest, is also satisfactory, and therefore may be the concluding form of the chord. But that in which the fifth is highest, does not completely satisfy the ear; it rather leads to the expectation of something to follow. Hence it is very proper in the beginning, or in the less formal closes in the middle of a strain, or at the end of a first strain, when another is to follow; but it is very sel dom found at the final close.
109. The examples which we have hitherto given, are in font' parts. In compositions of more than four parts, it is The student will observe, that in these examples, the im perfect chord on the seventh of the major scale, and second of the ininor, is treated the same way as the consonant common chords. On this account, some have even gone so far as to call this a consonant chord. But this is an abuse of language. The ear is reconciled to this free use of the imperfect chord, in such progressions, by the orderly suc cession of the chords. But the chord in question is truly a discord, and as such, generally receives that particular treat ment NN IliCh Will be explained afterwards. The student will
find a profitable exercise in writing and performing these progressions in different keys. Ile should write them in different positions, and varying the manner of beginning the progressions. Let him be very careful to avoid consecutive perfect concords in similar motion, and also to avoid taking a perfect concord after an imperfect, in similar 'notion, be tween the same parts. He will then see the reason why we have given several of these progressions in different ways. No. 7, is taken from Kollmann's New'Theory ; and the rea _der will observe, that in every second step, the third pro ceeds to the octave by similar motion between the bass and third part. IIere the procedure is so covered by the high er parts, as to give no offence. Indeed, when the upper part rises a single degree, and the bass rises a fourth, as in this example, the progression is sanctioned by the practice of the 'best authors. But in his first exercises, the student cannot be too strict in observing these rules. In No. 6, this is avoid ed by doubling the fifth of the chord rather than taking the octaN e.
III. The student must also be careful to dispose the se veral parts in an orderly and melodious manner. This is so well stated and exemplified by Mr. Kollmann, in his New Theory, that we shall copy his explanation and examples. " To connect intervals properly, it is required, either to keep every lepetition of a note in its former place, or to chang,e the notes of the different parts in sac!' a manner, that the ein may easily follow the progression of every part.
No. 1. is a progression by fundamental concords, where every repeated note is kept in its former place, and, conse quently, this example is most connected. No. 2. is the same progression ; but the parts changed in a melodious contrary motion. No. 3. is the same progression, but the parts tum bling about in an unmelodious manner, which is therefore not good." 112. One common chord may also succeed another dia tonically, that is, by one degree of the diatonic scale ; but then the parts must move in opposite directions. This pro gression often takes place from the dominant of the major mode to the relative minor, or from the dominant of the mi nor mode to the chord of the sixth of the scale ; and these progressions taking place in the proper part of the measure, form what are 'called interrupted cadences ; Nos. 1. and 2. of the examples following. When the subdominant chord rises diatonically to the dominant, it forms what Dr. Call cott names the mixed cadence; Nos. 3. and 4.