In the previous article you saw how the different voices of a chord evolved to get to another chord, following a very specific voice leading procedure, which is called a "forced" motion. And that's what we will see in detail today.
The two main such motions we saw last time were the movement of the third of the dominant chord (the key's leading-tone) a minor second towards the root of the tonic chord, and the movement of the seventh of the dominant chord downward a second minor towards the major third of the tonic chord. I know, that sounds pretty complicated, but if you analyze what I just wrote and go back to the previous article, you shouldn't have a problem wrapping your head around it. Although you should note that the example in question is of a major perfect cadence. In the case of a perfect minor cadence, the seventh of the dominant chord moves downward a major second towards the minor third of the tonic key.
The concept of the "forced" motion is intimately linked to that of attraction. The main example of this, and which we have already seen before in this series, is the leading-tone: the note one half step below the key's tonic. But it can also be a different note from the leading-tone which nevertheless creates a dissonant interval, as you saw in article 23.
Or even a chromatic note within a progression with the same name:
On the other hand, the strong attraction towards the first degree of the key experienced by the fifth degree is not a "forced motion." In fact, forced motions are always conjunct (refer to article 22).
Ordinary and exceptional resolutions
There are two forms of resolution: ordinary (regular) or exceptional (irregular). An ordinary resolution is what you usually think of a resolution: the move of a note or chord from dissonance to consonance. The example we mentioned in the previous article illustrates such a resolution.
Generally speaking, when it comes to ordinary resolutions, the following conjunct motions take place::
the fourth (mixed consonance, quasi-dissonance, see article 23) moves towards the third (a)
the diminished fifth (of the tritone) moves towards the third, following the double motion mentioned in the previous paragraph (b)
the augmented fifth moves towards the sixth (c)
the seventh also moves towards the sixth (d)
the ninth moves towards the eighth (e)
However, sometimes the forced motion of a note doesn't result in a consonance, but rather in a new dissonance aimed at suspending the arrival of the consonance expected. It's in such cases that exceptional resolutions take place, which is something we'll discuss in the next article. Just as we will also see later on, that for dissonances to be resolved they usually need to be prepared...
So be patient my friends, once we've covered this you'll be ready to start harmonizing your first melodies. I promise!