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ChoraleGUIDE: writing four-part harmony in the style of Bach

Method - Step 3b: Rewriting the bass

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This is where you turn your plodding series of root positions from step 2b into a proper bass line! You will change the bassline (and harmonies where necessary) in order to eliminate voice-leading problems and to create a strong melody that works well with the soprano and leads effectively into the fingerprints that you chose in the last step.

Beware! Only change the harmonies if it is necessary in order to create a good bass line - if you change them too much you will destroy the clear sense of key achieved in step 2b. Less is often more ...

What to aim for in a bass line ... ... how to achieve it
Apart from eliminating voice-leading errors (see the Double SLAP - in particular leaps, awkward intervals and parallels), the following basic guidelines summarise what you are trying to achieve in this step.

The bass should:

  • have a good balance of leaps and steps
  • not leap twice in the same direction (unless roots of I - V - I)
  • not have any repeated notes (other than in Ic - V - I)
  • not follow the top line too closely in either similar or parallel motion (there should be some contrary motion and as a rule of thumb don't move in parallel thirds or sixths for more than three notes in a row)
  • have some sense of shape and direction - avoid the 'siren' bassline that goes repeatedly between two or three notes!
In addition, you need to be aware of harmonic progressions that you should avoid - have a look at the DOs and DON'Ts of harmony.
In order to improve your bass line, you can do any of the following:
  • change to another primary chord (so long as it fits the melody)
  • change from root position to first inversion
  • add a passing note
  • replace a primary chord with VI or II (but see harmonic DOs and DON'Ts)
  • using a mid-phrase fingerprint (see resources - I - VIIb - Ib or Ib - VIIb - I are particularly effective)

In the example below, I have identified various problems with the primary chord harmonisation from the previous step (plus the fingerprints from Step 3a) and then made some changes to the bassline and harmonies in order to solve them. Notice how few changes you can make to make a massive improvement. Although it could be improved further, this is now a good bassline for a Bach chorale.

Problem Solution
The bass in the first bar has rather a lot of leaps. Although it is fine for basslines to leap, there should be a good balance of leaps and steps so that it is a melody rather than just a series of roots of chords Changing the V in the second beat to a first inversion chord creates a better bass line in which the first three notes are a bit more melodic and singable before the leap down to the C that leads into the fingerprint (obviously the leap in the perfect cadence is inevitable and not a problem)
The third bar starts with a repeated D - Bach virtually never repeats a bass note because it breaks up the flow of the music (the exceptions are between the pause note at the end of one phrase and the first note of the next and between an upbeat and the following downbeat at the very beginning of a chorale) Changing the V in the second beat to a first inversion and then joining the D and F# with a passing note makes for a more melodic bass line
There are parallel octaves from the end of the third bar into the beginning of the fourth Substituting the first G major chord of the fourth bar to a VIIb eliminates the parallels
The bass line in the second phrase is too leaping and repetitive Making the above change to VIIb and changing the next D major chord to a first inversion makes the bass line much more stepwise and gives the melody a better sense of direction.

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© Copyright Thomas Pankhurst