ABRSM Grade 6 Q1b: Adding Bass and Figures to a Soprano Line
In this lesson we will find out how to add a bass line and figures to a given soprano. In this type of question, you should not write in the alto and the tenor parts. A chord and bass note should be written for each asterisk.
The bass line needs to follow the normal voice leading characteristics of bass lines, which you can find in the section on Voice Leading.
- Use a mix of leaps and steps.
- Avoid using repeated bass notes, apart from in the Ic-Va progression.
- Make sure that any leading notes rise by a semitone step to the tonic.
- All melodic augmented intervals need to be avoided.
- Diminished intervals are allowed but need to be resolved correctly. (It may be easier to avoid them).
- Leaps of a 4th or 5th are normally into root position chords, and inverted chords are most often approached by step.
All of the diatonic chords in the key of the piece are potentially available to you, but this does not mean you have a completely free choice of chords. The chords you pick need to follow normal chord progressions.
You also need to use a good variety of chords in your bass line. (It is possible to harmonise any melody with only chords I, IV and V, the “primary” chords, but without any secondary chords the harmony will not be varied enough).
You also need to use a variety of inversions and treat cadences correctly.
The best way to the tackle this type of question is:
- Work out all the possible chords for each note.
- Choose the chords and inversions that make the best progressions and bass line.
To choose a chord that fits each melody note, start by assuming the melody note is a chord note (rather than a non-chord, decoration note). It is possible that notes in the soprano could be accented passing notes or appoggiaturas, but 99% of the time they are chord notes, so take this approach first.
Work out which chords each soprano note belongs to and write them down.
Now, starting from the final chord and working backwards, select each chord based on the most typical progression available, and also pick the inversion that makes the best bass line. Keep a note of which chords you’ve used in their Roman numeral notation as well as figured bass numbers, so you can make sure the progressions are good and that you’ve used a good variety of chords.
The final chord will be chord I in most cases, and the chord before this must create a proper cadence (usually a perfect cadence, V-I). Before chord V at a cadence, the most typical chords are Ic and iib, so use one of these if possible. (Most exam questions also have a cadence around half-way through.)
After that, aim to move smoothly (2nds or 3rds) into first and second inversion chords. Root position chords may be approached by any interval except the 6th or 7th and augmented intervals. Avoid repeated notes.
Root position chords should be left blank unless they are part of a cadential 6/4 progression. First inversion chords should be figured with a 6. Don’t forget to raise the leading note in chord V, where necessary.
Here is an example answer.