Direct fifths and direct octaves refer to a forbidden harmonic progression in music theory where two voices move in parallel motion to a perfect fifth or octave. This creates an undesirable sound because it lacks independence between the voices.
Unequal fifths: Unequal fifths are another type of forbidden harmonic progression where two voices move from one perfect fifth to another that is not exactly tuned. This creates a dissonant and unpleasant sound.
Parallel motion: Parallel motion refers to when two or more voices move in the same direction by the same interval. It can create strong harmony but should be used carefully to avoid unwanted effects.
Voice leading: Voice leading is the art of smoothly transitioning from one chord to another by moving each voice as little as possible. It helps create pleasing and logical progressions in music.