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A11. Adding a Figured Bassline

Grade Six Music Theory - Harmony Lesson 11: Adding a Figured Bassline (Question 1b)

In the grade six music theory exam, there are two questions which feature figured bass.

We previously looked at how to realize a figured bass, and earlier in this course we also looked at how to harmonize a melody. In this lesson we will look at the second figured bass questions: how to add a figured bass line, which is a combination of both! (This question is optional in the current grade 6 exams).

  • Realizing a figured bass means creating chords and melody from the given figures and bass line.
  • Harmonizing a melody means choosing chords to fit a given melody, and notating them with Roman numerals (e.g. Ib). You don't write out the bass line in the exam, but you need to work it out anyway!
  • Adding a figured bass line means choosing chords and a bassline to fit a given melody, and notating them with figured bass. The bass line must be written.

 

To create a figured bass line, you need to follow these three steps: 

  1. Choose chords which progress without breaking any rules (consecutives, doubling, etc.) and which follow common progressions and cadences
  2. Write out the bass line (i.e. the lowest note of each chord)
  3. Add figures where appropriate, to show exactly which chord the player should build on each bass note.

 

Steps 1 & 2

The steps to choosing chords are the same as detailed in the two lessons on harmonizing a melody. Re-read those units now if you need to refresh your memory. In a nutshell, the procedure is:

 

  1. Using the melody, identify which chords fit each note and write them down.
  2. Always start with chords I or V where possible.
  3. Use root position chords in a cadence.
  4. Use a variety of primary (I, IV, V) and secondary (II, VI, VII) chords. Use a different chord on each harmonized note. Make the roots of each chord rise/fall by a 5th when possible (e.g. VI-II).
  5. Pick each chord and inversion, paying attention to the tune being produced in the bass. Write the bass note and put the chord in Roman numerals for now. (We will delete the Roman numerals later). 

    You should:

    • aim for contrary motion with the melody where possible, and always when both the melody and bass line move by an interval of more than a 2nd
    • avoid augmented or diminished intervals in the bass melody
    • not write consecutive perfect 5ths or octaves
    • make the bass line move mostly by a mix of intervals of 2nds, 3rds, 4ths or 5ths
    • only write 2nd inversion (c) chords where there is a cadential or passing 6-4
    • avoid doubled major thirds, especially when it is the leading note (e.g. D-F#-A in G major, F# is the leading note and shouldn't be doubled)
    • avoid augmented chords (III+ in a minor key, e.g. C-E-G# in A minor)
    • not anticipate the harmony on a weak beat (e.g. Ia – Ib with Ia on a weaker beat)

 

Step 3

Putting in the Figures.

You must follow the conventions for figured bass. The rules are:

 

  • Root position (5-3) chords should be left blank UNLESS they are part of a 6-4 progression (cadential 6-4), in which case write 5-3.
  • First inversion chords (6-3) should be marked with just a 6
  • Second inversion chords (6-4) should be marked 6-4
  • In a minor key, you will often need to add accidentals to a chord, for example chord V should be major. In the figure, the accidental is written next to the number it affects, e.g. 6#. An accidental without a number refers to 3. For example, a # on its own is used as a short-hand way of writing 5-3#. 

 

Here is a worked example.

We are going to add a figured bass to this melody, assuming there is a change of chord with each star.

adding-a-figured-bass-line-question

Notice that it starts on an A natural – this is an excellent clue that the piece is in D major, and not B minor. In B minor we would expect the leading note A to be raised to A#. We need to use chords I and V at the start, to fix the key properly.

1-use-i-and-v-to-fix-key

We will add an imperfect cadence at the end. The last-but-one chord could be I or vi, so we'll note down both options for now.

2-imperfect-cadence

Now to continue from bar 1. The note B fits with chord IV, which is a root fall of a fifth (D down to G), so therefore it makes a strong progression. I-ii is also ok. I-vi is a weaker progression because the roots move by a 3rd (D-B), which means the chords share two notes (D and F# in this case). I choose IV, because it is a primary chord with a strong root progression.

3-iv-strong-root-primary

The note A fits with V and I (remember that iii isn't normally used). I choose chord V, because the progression I-IV-V is more varied than I-IV-I.

4-v-for-variety

The note G fits with ii, IV and vii°. V-vii° is a root movement of a third (2 notes in common). V-IV is a root movement of a step (ok) and V-ii is a root movement of a 5th (strong), so I choose ii for this chord. In this bar, I can continue the progression of 5ths with ii-V-I. The second G in the bar can be treated as an accented passing note (between F# and A, but played on the beat). Most of the time melodic decoration will be unaccented, but always be aware that you could interpret some decoration as accented instead, which will open up more chord possibilities.

5-accented-passing-note

The note A fits with I, V and iii. We don't normally use iii, which means using a different inversion of I, or using V. I choose V.

6-v

The next chord has to fit both B and D. The C# is a passing note. This gives us the option of IV or vi. I choose vi, because I haven't used it yet elsewhere.

7-vi

Finally, the notes C# and E need to fit with the next chord. This gives us V or vii°. Both of these chords lead to I, so we will pencil in both of them, and change the next chord to a definite I.

8-v-or-vii-to-i

The next step is to work out which inversions are best. Remember:

• no consecutive 5ths and octaves with the melody

• no augmented or diminished intervals

• no second inversions except at a cadential or passing 6-4

• don't use Va-vib

• the leading note must lead to the tonic

• no leaps of a 7th

Start at the beginning and with each inversion you choose, check it with its neighbouring chords to make sure none of the above rules are broken. For example, you can't begin this piece with Va-Ia, because it would create consecutive octaves with the melody.

Write in ALL of the figured bass figures as you are working out your answer, including the 5-3 chords. This will help you to keep track of where you are. Erase all unnecessary figures when you have finished: all 5-3's except those in a cadential 6-4, the "3" of 6-3's. Make sure you have included any necessary accidentals (in minor keys). Here is a possible answer:

9-added-figured-bass-line

And this is what it could sound like with the alto and tenor parts completed, and some additional melodic decoration added! You shouldn't fill out these parts in the exam - this is just for illustration.

 

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