Does the three chord trick always end a chord progression on the third chord?

Question

It seems almost a redundant question, but the meat of it is this:

If one is using the three chord trick, is it stylistically required by rules of theory and phrasing to end the progression on the third chord? While it is pleasing to the ear to complete the phrase and repeat after three chords, will extending the phrase cause major disharmony or dissonance? What concepts of music theory can be cited to support this?

Answer 1

No. In fact, ending a passage of music on the third chord (the dominant) is an imperfect cadence or half cadence. As implied by the name, there is a "better sounding" perfect cadence (or authentic cadence), where you end on the first chord (the tonic). To quote Wikipedia:

Because it sounds incomplete or "suspended", a half cadence is considered a weak cadence.

_{http://en.wikipedia.org/wiki/Cadence_(music)}

The concept of finality is, of course, subjective; but as for dissonance, that is not present regardless of the order the chords are played. The three chords (tonic, dominant, subdominant) are the main chords of the key and are so often used exactly because they don't clash with each other.