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Victoria Williams

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Figured Bass Lesson 7: Choosing the Chords and Writing the Figures

Grade 7 Music Theory Q1 Figured Bass. Lesson 7: Choosing the Chords and Writing the Figures

Working out which chord to use is the tricky part of figuring a bass. You need to keep in mind quite a lot of information:

  • Work out what key the piece is in and make a note of any apparent modulations.
  • Pick a chord which both the melody and bass is part of.
  • Make sure that the inversion is allowed.
  • Make sure that the progression is stylistically correct.
  • Do the easy parts first and leave difficult chords until the end.
  • Look for clues like a static bass line, or leading note/tonic in the melody.
  • Look for patterns in the harmony, and keep them going when possible.

 

Cadences, Suspensions and V-I's First

First scan through the piece looking for places where it's obvious that a cadence or suspension is needed. Cadences always happen at the end of a piece of course, but often they happen in the middle too.

Also look for other places where a leading note rises to a tonic; use V-I in these places, or possibly a V substitute (but don't use a V substitute at a cadence!)

Look for places where the bass line is static (or moves by an octave) but the melody moves by step – these are the places where cadential 6-4s and suspensions will be needed. (Don't forget that suspensions need to be prepared). Do these first.

Here are the last two bars of a piece in A minor:

cadence

We will need a perfect cadence at the end, so we know that Va-ia will be the last two chords. The bass line has two E's an octave apart, which is a clue that a cadential 6-4 will work. We can put the ic-Va-ia figures in, remembering to sharpen the 3rd in chord V. Also, don't forget to write out 5-3 in full, because it follows a 6-4 chord.

Notice that there are two more places where the bass line is static:

static-bass

In both of these cases you could use either a Ic-Va progression, or a suspension.

  • The first shaded chord fits ic-Va in A minor, and the second shaded chord fits Ic-Va in the relative major key of C – it's a very brief modulation.
  • Or if you prefer, each shaded chord has a dissonant interval of a 4th which falls to a consonant 3rd, so you could use the suspension figures 4-3. (Notice that 4-3 is actually part of the figure 6/4 – 5/3 anyway – the two progressions are very close).

static-bass-figured

 

The Rest of the Piece

When you've finished with the cadences and suspensions, work through the rest of the piece. Here's another bar to work through together, (the key is G minor). The chord we are working on is shaded.

chord-1

We need a chord with D and A in it. The only possible chord is V. Because it's a minor key, chord V will usually be major (D major). D is the bass note, so it's root position. We need to add a # for the third.

chord-2

The chord must contain C and Eb. Two chords contain these notes, C minor (iv) and A diminished (ii°). We will move on and see if the subsequent chords affect our choice.

chord-3

We only have a D – it could be chord V, III or i. We will come back to this one too.

chord-4

The chord must contain Eb and C. Only C minor (iv) is possible here, because the other chord with these notes in is A diminished, which is best used only in first inversion. As Eb is the bass note, it must be ivb.

chord-5

D and Bb are in chord i and chord III (Bb major). Chord i would be in 2nd inversion, so chord III is the better choice. The bass note is D, so it's first inversion. Watch out though – we've already sharpened the F's in this bar with the first accidental, so we need a natural sign to make sure that the chord is Bb major and not Bb augmented!

chord-6

C and A are part of chord A dim (ii°), and F major (VII). F major would be 2nd inversion and A dim would be first – so A dim is the correct chord.

Now let's go back to the chords we missed, and write in the Roman numerals so we can see what's happening with the chord progressions:

chord-2-and-3-again

We could choose from any of these progressions for these two chords: IV-V, ii°-V, IV-III, ii°-III. Remember to pick the most likely progression – in this case IV-V and ii°-V are common. Since we've got ii° already at the end of the bar, IV-V will be more effective. Both are root position chords, so we just need to add a # on to chord V.

finished-chords

 

 

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