Harmony and voice leading

Listen vertically and horizontally

Play two chords, then isolate the highest note from each. You have revealed a short melody inside the progression. Repeat with the lowest notes and an inner part. A progression that looks straightforward as chord symbols can contain awkward leaps or a striking countermelody when its individual lines are heard. Voice leading asks you to pay attention to both the combined sound and the paths that create it.

For a singer, the next note must be heard and reached; for a guitarist, a new shape must be playable; for a synthesizer arrangement, register and overlap remain audible even when fingers are not a limitation. Write each part on its own line before judging the whole. If a part has no clear identity, decide whether it should sustain, move or disappear rather than adding notes by habit.

References: [1]

Describe how the parts move

Two parts moving in opposite directions use contrary motion. If one stays while the other moves, their relationship is oblique. If both travel upward or both downward, it is similar motion; parallel motion retains the same interval type between the lines as they move. These descriptions let you discuss an arrangement more precisely than saying the chords feel 'smooth' or 'big'.

Try a lower line C3–D3 and an upper line G4–F4: they move in contrary directions. Change the upper line to G4–G4 for oblique motion. Then try G4–A4, producing parallel perfect fifths when octave displacement is taken into account. The last choice has a distinct audible effect. Whether it is desirable depends on the style and the intended degree of independence between parts.

References: [2]

Separate harmonic function from physical movement

In common-practice tonal harmony, tonic, predominant and dominant describe different roles in a progression. In C major, C can act as tonic, F or D minor as predominant, and G as dominant. A familiar movement is from departure through dominant tension to tonic arrival. Those labels describe an established tonal grammar; they are not an account of all music organised around pitch.

A functional progression can be voiced with large jumps, while a nonfunctional succession can connect through very small motions. Test the two decisions independently. First choose the chord sequence and listen to its direction; then choose how each part travels. If a melody requires a conspicuous leap, let it leap and keep another part stable if that serves the arrangement. Small movement is a useful option, not the only expressive aim.

References: [3]

Choose a voicing, then audit each line

Begin with the notes that can remain unchanged between two chords. Assign those common tones to a sustained part if you want continuity, then move other parts to available notes. Check that no necessary chord member has vanished accidentally. Listen for a doubled note that dominates the colour or a close low-register interval that obscures the bass. Revise by ear as well as on paper.

Historical part-writing exercises use additional rules about spacing, doubling and parallel perfect intervals. Study those rules when learning the relevant style, with their reasons and exceptions. Do not carry them unexamined into every popular arrangement, drone-based performance or experimental texture. State the goal: independent choir parts, a unified guitar riff and a dense electronic cluster may call for different decisions.

References: [1]

What to remember

• A progression contains individual melodies as well as chord names.
• Check harmonic function and voice motion separately.
• Judge a voicing against its musical purpose and style.