OF THE :MOVEMENT OF CONCORDS; OF COMMON CHORDS, THEIR SPECIES, POSITIONS, AND PROGRESSIONS OF THE DERIVATIVES OF COMMON CHORDS, AND THEIR PROGRES SIONS.
94. A succession of single musical sounds, duly ordered in respect oldie intervals, limns melody or song. T WO or more musical sounds, differing by proper intervals, heard at the same time, form a chord; and a proper succession of chords forms harmony. The union of melody and harmony forms the best music. These two branches of the musical art must be considered separately, to a certain extent; but neither can be thoroughly understood without a knowledge of the other. Of these two branches, harmony is capable of more precise rules than the other. We shall therefore endeavour to make the student acquainted with the most simple, and at the same time the most important of these, before we attempt to investigate the nature of melody-.
95. Alusical intervals are either concords or discords. 'The octave, the major fifth, the major and minor thirds, the major anti minor sixths, ate concords, and are pleasing in themselves. The seconds, major and minor, the seventh:, major and minor, the minor fifth and major fourth, are di, cords ; they are not so pleasing in themselves, but they ate much used in harmony, and greatly heic_dnen its effects. It has been much disputed whether the minor fourth (the in version of the major fifth) oug.ht to be ranked among the concords or among the discords.. There can be no doubt that in many combinations it is truly concordant. OH the other hand, in some situations and combinations, it is felt to be a discord, and treated according.ly: but this the student will understand better bye and by-e.
The unison is the most perfect relation that subsists among musiCal sounds, and it may, without impropriety, be called a perfect consonance or concord. The octave is next after the unison, the most perfect concord, and the major fifth the next in point of perfection; it is therefore usually' called the perfect fifth, which name, as being familiar with musicians, we sitall generally- use hereafter. 'The minor fifth, in con tradistinction, is usually called the imperfect fifth, or disso nant fifth, or fatse fifth; and these expressions we shall also use as synonymous.
97. The unison, the octave, and the perfect fifth, are called perfect concords. Thirds and sixths, major and minor, are called imperfect concords. It is necessary to keep this distinction in mind, in order to understand the rules laid down for the succession of intervals between two parts.
98. These general rules we shall give immediately; but it is necessary first to explain the different kinds of motion. When two parts both ascend, or both descend at the same time, they are said to go in similarmotion. When one part remains at the same pitch, while the other ascends or de scends, the motion is called oblique. When one part ascends, and the other descends, the motion is called contrary.
99. The first rule for the movement of concords is, that there must not be two perfect concords in succession, be t ween the same parts, by. similar motion. These are tech nically termed, consecutive octaves; and octaves in succes sion are forbidden, because they produce no good effect, and fifths, because they produce a very bad one.
N. B. This rule does not respect two or more instruments or voices, movina tog,ether in unison or octaves, in the sante melody, which is called doubling the part, and is univer sally practised.
The second rule is, that you must not go from an imper fect concord, to a perfect concord, by similar motion. These passages are said to contain hidden octaN es or fifths, which are made apparent by filling up the diatonic degrees through which one of the parts is conceived to pass; which cannot take place when the parts move in contrary directions, as is shown by these examples.
WO. These rules will be fully illustrated in the sequel. In the mean time we shall quote from .1r. Shield's excellent Introduction to Harmony, his directions for the management of the unison, and of the fifth. " When both parts move, it is better to go from the unison to the third minor, than to go to the major. To the minor we may go either by oblique, or by contrary motion; Ex. 1st. But to the major we must, by oblique, or by similar motion: the first is the best; Ex 2d.