ABSTRACT
Voice-leading regulations are vital in shaping common-practice tonality, but composers treat them flexibly. Two voices an octave apart that move in parallel motion exhibit little if any independence. The single voice is strengthened by a richer timbre, but no attempt is made to imply two or more independent parts. Parallels formed by more than two voices are considered unproblematic. Notice that the block-chord reduction reveals a new set of parallel octaves between the soprano and tenor. The bass and soprano coalesce into a single voice, while the inner voices remain independent and distinct. It may appear that the outer voices form dubious parallel octaves. The sense of closure generated by harmonic, rhythmic, and other factors can be enhanced when two voices, often the outer voices, traverse similar melodic trajectories. Unequal fifths occur when two voices form a perfect fifth–diminished fifth or diminished fifth–perfect fifth succession.
