This lesson refers to the keyboard reconstruction question (Q2. ABRSM Grade 8 Music Theory).
Voice Leading and Consecutives
Although you are writing for piano rather than in four part harmony, you should still think about how the individual strands of melody move. Think about your piece in terms of a melody, bass line, and any inner parts, and pay careful attention to the voice leading of each.
Within a single part, the musical line should move smoothly and consistently.
Generally, each individual line should move mostly by small intervals – 2nds and 3rds for example, although there willl also normally be places where a leap will be suitable. Do not leap around with a good reason.
The leading note, will nearly always be best rising by a semitone to the tonic, when the harmony is V-I. The leading note can fall to the dominant in an inner part, but this much less common in piano music than vocal. Avoid moving from the leading note to the mediant, unless there is a very good reason to do so.
Unlike in vocal music, the parts can move by an augmented or diminished interval, but because this type of movement is dissonant, you should always resolve the dissonance afterwards.
Many dissonant intervals contain a leading note. The leading note should rise, and the other note should fall, also by step. You can either play both resolution notes together, or separately, but if you miss one out, the dissonance will be left partly unresolved, which can sound awkward. In minor keys there is also a dissonance between the supertonic and submediant – this works the same way, with both parts moving in opposite directions by step, to a consonance.
In this extract which is from Mozart’s piano sonata no 19, notice how smoothly each individual line moves. Whenever there is a leading note (E), it resolves upwards by a semitone to the nearest tonic F, and elsewhere, the vast majority of melodic movement is also by step (semitones or tones). Although this is a keyboard piece, you can look at it as a piece of 3 and 4-part harmony, to see how the voice-leading of the individual parts is handled.
Let’s look at how this knowledge works in practice. Look at the empty bar in this extract from “First Loss” by Schumann, and think about what would be needed next, to continue the left hand.
The key is E minor, so the end of the second bar here belongs to dominant chord, B major, and we would expect the next chord to be a tonic E minor.
The clef changes from treble to bass, so this is a clue that we are expected to write something at a generally lower pitch than before.
The D# in the B major chord is a leading note, so it needs to be followed by a tonic E – but there are 3 E’s that fit comfortably within the bass clef stave, so which E should it be?
It should be the E a semitone higher than the D# in the B major chord, so we need the E on 2 ledger lines, to make the voice leading correct:
Here is another extract from later in the same piece. The F naturals show us that the key has changed, either to C major, or A minor. The single quaver (8th) rest at the end of the 2nd bar here, suggests that you need both hands to play something for the next chord, then the left hand falls silent for a few beats.
If we analyse the harmony, we can see that the chords are probably C, F and B diminished, i.e. I, IV and vii in C major, although you could interpret them as A minor, F and B diminished or I, vi and ii in A minor – both keys work, but I think the C major approach is better because if it was A minor, the tonic chord would have no root, so let’s do this in C major.
Chord vii is normally followed by a tonic chord. The B is the leading note, so it needs to rise to C. The F makes a dissonance with the B, so this needs to be resolved, downwards to E, and the D in the left hand would be best falling to C. If it rises to E, the 3rd is doubled in the chord, which is not ideal in 3-part harmony, and it cannot fall to G because it is not a suitable place for a 2nd inversion chord.
Think about the rules of doubling and omissions in the same way that you do in 4-part harmony. Follow the normal rules where possible, for example, avoid doubling the leading note or 7th, and always aim to include the root and third as a minimum of any chord.
Consecutives
You need to avoid all consecutive perfect 5ths, (unless they have already been used in the given material and are important for the overall style). A perfect 5th can be followed by a diminished 5th, but avoid the opposite direction because the dissonance inside it does not resolve properly.
Consecutive octaves are very common in keyboard music, as they are useful for reinforcing the sound, or “doubling the melody”. This is from Beethoven’s Piano Sonata no.15:
The right hand moves in octaves, but these are fine because the octaves just reinforce the melody. The lower note in each octave does not belong to a separate, individual voice.
This is Schubert’s Impromptu in A flat major.
Consecutive octaves must be avoided however, when they occur in independent parts.
This is an example of illegal octaves – the consecutives are from G to F in the soprano and bass. The music is has three independent parts – bass, tenor and soprano.
