====== Two-Part Counterpoint ======
===== Third Order: Four Notes Against One =====
==== Rule 17 ====

In this order ((species)) of counterpoint, each of the two portions of the bar -- the accented as well as the unaccented -- are divided by two crotchets ((quarter notes)).

To be in conformity with the style of the ancient composers, it is necessary, respecting these crotchets ((quarter notes)), to employ, as much as possible, conjunct movement, in preference to disjunct movememnt.

==== Rule 18 ====

The first crotchet ((quarter note)) in the accented part of the bar should always be a concord ((quarter note)); the second, the third, and the fourth crotchet ((quarter note)) may be alternately consonant and dissonant, provided each discord ((dissonance)) come between two concords ((consonances)), and that the melody progress by conjunct movement, as well ascending, as descending.

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When the counterpoint is made to proceed by disjunct movement, the sounds which progress by this movement must all be consonant:--

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Upon examining these examples, they will be found twice to contain the unison; this seems at first sight a fault, but in the present order ((species)), the unison is tolerated, on account of the slight value of the notes -- excepting, however, at the commencement of each bar.

> **Supplementary digression** -- When the second crotchet ((quarter note)) of the first portion, and even of each portion, is dissonant, the ancient contrapuntists occasionally passed to the concord ((consonance)) by a movement of a third, ascending or descending.

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By the multiplied examples of this exception to the rule met with in classical authors, and the reiterated use made of it by them, there is warrant for thinking that this license may be converted into a precept. But what end would the present rule serve, were a method admitted that should destroy its effect? Better far, that such a license should neither be admitted nor tolerated in strict counterpoint. These different passages from the old composers are submitted for the inspection of the pupils, in order that they may know what to believe, when, in examining the works of the Classics, they come to passages where this license has been practised. There is no tradition which transmits the reason why these same Classics thus faultily deviated from the rule. There is no comprehending why, instead of doing thus:--

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as in this case:--

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In this latter example are two discords ((dissonances)) which succeed each other, and which brave the rule; but it is permitted in certain cases to use them thus, provided these discords ((dissonances)) succeed each other by conjunct movement: occasionally, similar passages will be met with, where it is necessary to introduce two discords ((dissonances)) in succession. To return to what has been said above, there is no reason which may excuse the classics for having employed discords by disjunct movement, if it be not that, for the sake of greater variety, and in consideration of the small value of crotchets ((quarter notes)), they caused the discord ((dissonance)) to leap by the interval of a third, which is the smallest -- with the exception of a second -- and consequently easier of intonation.

==== Rule 19 ====

Neither a single crotchet ((quarter note)), nor two, nor sometimes even three crotchets ((quarter notes)) in two-part counterpoint avail to save two parallel fifths or octaves; although in certain cases, contrary movement is employed, or a leap greater than a third.

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==== Rule 20 ====

If in the preceding orders ((species)) of the two-part counterpoint, leaps of a major sixth, or minor sixth, and those of a tritone and of a false fifth have been prohibited, they are still more strictly forbidden in the present order ((species)), on account of the slight value of the notes, and of the short time which the voice has to prepare for assuring the intonation of harsh intervals.

The interval of tritone must also be avoided as hard of intonation, and as disagreeable to the ear; even then it can be reached by filling in with conjunct sounds, ascending or descending.

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The harshness of these passages arises from the circumstance, that the B and the F always occur at the extremes of pitch in the lower or upper points of the melody; and as the extreme sounds make more-immediate appeal to the ear than the intervening sounds, it follows that the ear, in the cases here shown, is sensible of the harshness of the tritone, while the other sounds can neither totally efface it, nor even effectually dissipate it.

There are cases where the tritone, ascending or descending by gradual notes, may be introduced, without the objection denoted in the above example. It is when the two sounds which form the interval of tritone, do not occur at the two extremities of the melody, and are thus contained in a series of conjunct sounds.

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It will be seen by these two examples, that the tritone is concealed between the two extreme sounds, with very softened effect; and that by this means the disagreeable impression it produces, is far less perceptible, if not altogether destroyed.

==== Rule 21 ====

In this order of counterpoint, in the same way as in the preceding order, a rest at the first bar of the part which forms the counterpoint, may be used; this rest will be of no longer duration than a crotchet ((quarter note)), and the note which follows it must be a concord ((consonance)).

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==== Rule 22 ====

In the bar before the last, the first crotchet of the counterpoint should be a third, if possible. If the counterpoint lie in the upper part, it will ascend by degrees to the octave or unison of the last bar; and if the counterpoint lie in the lower part, it will descend by an interval of a third, again to ascend by degrees to the octave or unison of the last bar.

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This rule is not stringent; and another method may be pursued when the //cantus firmus// is so constructed as not of necessity to demand this procedure.

In concluding this present order ((species)), a model of four crotchets ((quarter notes)) against a semibreve ((whole note)) is subjoined.

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