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We have previously looked briefly at scoring music in four parts for SATB voices, and we touched some the issues related to harmonies in many parts. Now we'll look into these issues further, in the context of chord inversions and harmonising cadences.
Rules, rules, rules
Often, writing harmony in four parts can seem almost like a Sudoku puzzle, because you will be told so many rules to follow that it can sometimes seem impossible to obey (or even remember) them all. Good technique for writing harmony in four parts depends on many elements, including style and orchestration (if not for four-part SATB choir).
We will limit the rules and suggestions presented here to basic principles that should be followed in almost all circumstances, and each is illustrated with a star-shaped bullet point like this:
- Always observe these basic principles when writing four-part harmony!
In the SATB scoring section of Chords, we considered how to write three-note chords in four parts, which will by necessity involve one of the three notes being repeated: doubling. We gave a simple rule, to which we will add a further suggestion:
- Double the root of the chord in preference to any other note
- Double the note in the bass
For triads in root position, these amount to the same thing, but with chords in inversions the two rules contradict each other.
There are many solutions to this. For instance, we tend not to double the note on the 7th degree (the leading note), which is the third of the dominant chord - so if this note were in the bass, we would not double it, and we would attempt to double the root instead.
Ironically, a very important part of writing harmony is the melodic element! Each constituent part in harmonic music should have its own "melody" which makes sense as such:
- Always attempt to make each part follow a clear, "singable" line, mostly moving in steps of the scale and avoiding large leaps
The term voice-leading refers to the "singability" of a line; good voice-leading implies a very singable, melodic line and poor voice-leading implies a difficult, angular line that does not make any sense as a standalone melody.
Notice that in the example below, the soprano part and tenor parts move only by step, while the alto even stays on the same note throughout!
It is common in four-part writing for there to be a "least interesting" part, and that part is usually put in the middle of the texture: for either alto or tenor (in the example above it is clearly the alto!). The soprano usually gets a more interesting, more traditionally "melodic" part, i.e. "the tune".
The bass is the exception. Due to the special role of the bass in the definition of harmonies, it is expected that the bass will tend to move by leaps much more than the other parts – especially moving by fourths and fifths.
Notice that moving between the tonic in root position and either of the two other primary triads (
V) in root position necessarily involves motion by fourth or fifth for the bass.
IV, the bass must rise by a fourth or fall by a fifth. Moving from
V, the bass must rise by a fifth or fall by a fourth. Therefore we can say:
- The bass may commonly move by a fourth or a fifth to suit the harmony, in addition to step-wise movement
Regarding the general spacing of chords between the parts:
- Aim to space chords such that the widest interval between notes is at the bottom of the chord
The following examples show some well-spaced and some less well-spaced chords:
When writing music in four parts for voices, you will need to keep the notes for each part within the comfortable range for each voice.
In general, if you always write within the stave, you will be quite safe, but the best idea is to learn the ranges, as shown here:
Apart from merely setting notes within these limits, a good technique will set each voice in the same part of their register: all high or all low, for instance. This is a secondary consideration, but will ensure the chord is well-balanced.
Often when writing parts, you will find that two parts will need to move in the same direction at the same time. This is called parellel motion, and if two parts move strictly in parallel, then there will be the same constant interval between them.
In itself, parallel motion is not a crime. However, some strong intervals should not appear in parallel motion. In particular:
- Avoid parallel fifths and parallel octaves
It may be helpful to think of this as a rule for keeping the parts independent. Parallel octaves in particular sound like two voices playing the same part, which is fine in some circumstances (for example, when writing for strings), but when the focus is on four independent parts, parallel octaves can cause one of the parts to apparently disappear temporarily!
Parallel fifths can sound very ugly in the middle of an otherwise free-flowing texture, which is why they, too, must be avoided.
Parallel fifths and octaves can sometimes be quite hard to spot, particularly between soprano and bass or between alto and tenor, and they are easy to accidentally write if you aren't careful. The following advice will help minimise the chances of this happening:
- Always aim for contrary motion between the upper (S+A) and lower (T+B) parts
If the upper parts (soprano and alto) are moving in opposite directions to the lower parts (tenor and bass), they will clearly not be able to fall into parallel fifths or octaves. This leaves only the chance of parallel motion between the soprano and alto, and the tenor and bass to watch out for, which is much easier as they share a stave.
Not every single note in a piece has to belong to the harmonies around it, and interesting music will frequently introduce "wrong" notes for embellishment and effect. Two common kinds of such extra notes are auxiliary notes and passing notes.
Frequently in music, there will be a note which belongs to the harmony which then moves by step to a note which does not belong the harmony before returning to the original, harmonic note. The non-harmonic note in the middle is called an auxiliary note.
See the beginning of Silent Night, below. The music is in D major; the harmony is in the tonic (
I) throughout the first bar, and the B in the soprano part does not belong in a triad of
I in D major (D, F sharp, A). It is an auxiliary note, because it moves away from then returns to a harmonic note (A, in this case).
We can summarise the use of auxiliary notes as follows:
- An auxiliary note is a non-harmonic note that must lie between two harmonic notes of the same pitch, with the same unchanging underlying harmony.
Auxiliary notes and the mordent
The auxiliary note is related to the ornament called the mordent, which is discussed in detail in Ornaments - but essentially, auxiliary notes are equivalent to carefully written-out mordents.
Where a melodic part moves by step from a harmonic note in one chord to a harmonic note in the following chord, it may pass through one or more non-harmonic notes. These notes are called passing notes, and are perhaps easier to see by example than by description.
Look at the following simple example, and in particular at how the indicated passing notes are not part of the "correct" harmony:
In the example above, the note C marked with an "x" is not strictly a passing note, if we consider the harmony to be
V7, yet it might appear to be, if we had considered the harmony to be merely
Accented and unaccented passing notes
Passing notes are of two main types: accented passing notes and unaccented passing notes. Accented passing notes are those that appear on a strong position in the beat - stronger than the following harmony note - and unaccented passing notes, by contrast, are paired with stronger harmonic notes.
Every accented note is followed by an unaccented note; this returns to the basic rhythmic idea of strong-weak pairs.
This leads us to the following rule when using passing notes:
- A passing note must always be preceded or followed by a harmonic note. If there is an accented passing note, then it must be followed by an unaccented harmonic note; if there is an unaccented passing note, it must be preceded by an accented harmonic note.
Here is an example of some music by Mozart with passing notes. The accented and unaccented passing notes are indicated:
In the Mozart example above, the accented and unaccented passing notes are marked with a and u respectively. The changing emphasis of accented and unaccented, for example in the descending scale in bar 3, give the music a very lively sense, and this shifting of emphasis is a subtle yet clever trick by the composer.
The idea of passing notes is somewhat extended when writing either in triple time, when writing triplets, or when writing in groups of three in compound time. In this case, there is an accented note followed by two unaccented notes (strong-weak-weak), and in this case it is acceptable to have unaccented passing notes on both of the "weak" notes, providing that they eventually reach a harmonic note in the next beat.
Here is an example that uses passing notes in triple time:
Look again at this example. You should be able to spot four examples of auxiliary notes as well as the many passing notes!
Passing notes and grace notes
Just as auxiliary notes are related to the mordent, passing notes also are related to an ornament: grace notes, or the appoggiatura and acciaccatura.
These, too, will be discussed in detail in Ornaments.