In counterpoint, the functional independence of voices is the prime concern. The violation of this principle leads to special effects, which are avoided in counterpoint. In organ registers, certain interval combinations and chords are activated by a single key so that playing a melody results in parallel voice leading.
The core concept is that in counterpoint, voices should function independently, while special effects are avoided. In organ registers, the activation of certain chords and intervals by a single key leads to parallel voice leading.