Voice-leading in Bach chorales: Spacing
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Vocal music sounds different depending on how the parts are spaced. If you write the middle parts very high when you are harmonising a chorale melody, the texture will sound thinner (and the voices more strained!) and if they are very low, the texture will be much darker and thicker:
Composers try to avoid very low and thick textures in choral writing, because the chords become very muddy and unclear. If you keep within the natural ranges of the four voices, it is unlikely that you will write a texture that is too high.
What should the spacing be in a Bach chorale?
The basic rule when writing a chorale melody is that the top three parts should generally be as close as possible. If there is a large gap it should be between the bass and the tenor parts.
You should follow these two basic guidelines:
- in each phrase the gap between tenor and soprano must be no more than a 12th (an octave and a fifth) at any point and less than an octave at some point *
- there should not be a gap of more than an octave between Soprano and Alto or Alto and Tenor
*this is the definition of a 'good' texture in the Exexcel mark scheme
Note how the tenor line is higher than you might think - mostly up in the ledger lines.
If the soprano is very low, all four parts may be much closer than would otherwise be advisable. The first of the two examples below is fine, because the soprano forces all the other parts to be low. In the second example, in which the soprano is an octave higher - the texture sounds unbalanced with the thick texture of the lower parts a long way from the higher top part. You can see that this breaks Edexcel's rule that the tenor should not be more than a 12th and at some point an octave in a given phrase.
What else should I avoid?
The voice parts in a Bach chorale should not generally cross, as this can disrupt the balance and clarity of the texture. Bach does occasionally cross the inner two parts (alto and tenor) in order to avoid parallels, but this is not a good idea in an exam. In this example, the alto moves unnecessarily below the tenor - it is easy to do by mistake when one or other of the inner parts is on ledger lines.