How to realize a figured bass

Question

I am arranging a Bach piece. I know, what the challenge it is to do it. But I have been able to successfully arrange Mozart and later, Beethoven, so I think I'm ready.

But here is the challenge I am running into right now. How to realize a figured bass into full chords? I know some things about figured bass realization like:

1. If you don't see any numbers, the chord is in root position
2. If you see just a 6, the chord is in first inversion
3. If you see a 6 and a 4, the chord is in second inversion
4. 7 for root position, 6 and 5 for first inversion, 4 and 3 for second inversion, and 4 and 2 for third inversion when it comes to seventh chords
5. No accidental means you just play a diatonic chord
6. An accidental instead of a number means that the accidental applies to the third
7. A slash through a number means to raise it a half step(so Bb becomes B, E becomes F, etc.)
8. An accidental next to a number means that you apply the accidental to whatever interval above the bass the number corresponds to
9. A number with a line means you suspend the note across the chord change(whether you rearticulate or tie the suspended note is up to you)

And I know some things about voice leading like:

1. Avoid leaps as much as possible
2. When you have to leap in a given voice, either go back in the opposite direction or form an arpeggio
3. Avoid intervals greater than an octave between 2 consecutive voices unless necessary
4. Never leap by an augmented or diminished interval, ever
5. Resolve tendency tones(so 4 to 3, 7 to 6 if 7 isn't the leading tone, 2 to 3, 7 to 1 if 7 is the leading tone)
6. Avoid unequal fifths in the outer voices(perfect fifth becoming a tritone for example)
7. No PPI's(parallel perfect intervals)
8. If you have to string together dissonances, no more than 4 before a resolution, preferably fewer
9. Parallel thirds and sixths are okay but if you have 4 or more in a row, they start sounding dependent
10. No tritones or other augmented or diminished intervals between outer voices unless a diminished 7th chord is specifically called for. It will just sound too dissonant to be acceptable

How do I go from these figured bass and voice leading rules and a bass line with figures to full 4 part chords? Is there a shortcut to finding a solution for any bass line and figures?

Answer 1

One hint: The figured bass realization doesn't need to have full four-part chords all the time. Most written-out realizations are far too busy and detract from the other parts rather than supporting them. Also, a realization that works well for harpsichord, or piano, or organ probably won't work nearly as well for either of the other two instruments.

I have a copy of Continuo Playing According to Handel, which I have found most informative.

But, obligatory snarky comment:

How to realize a figured bass into full chords?

Hire a well trained harpsichordist.

Answer 2

I’d say there is no short cut, except of playing Bachs figured Bach (e.g. keyboard accompaniment of Cantatas and Chorals) and compare it with the rules.

You will find that Bach broke the rules as the figured bass accompaniment was not always following the strict four voice-leading rules. So when you have played some accompaniments like Jesu Joy of man’s desiring, Bist du bei mir, Komm süsser Tod, or the accompaniment of the violin concertos you will get the ear and understand the language.

It is the same as learning a new language: you know the grammar and the vocabulary, but there is no short cut than to speak and apply the language.

This is what I am still working on.

So it will be a long way:

http://www.bach-cantatas.com/Scores/IndexScores3.htm

http://www.bach-cantatas.com/Vocal/BWV439-507.htm

copied from:

Bach JOURNAL ARTICLE The Figured-bass Accompaniment in Bach's Time: A Brief Summary of Its Development and An Examination of Its Use, Together With a Sample Realization, Part I Marla Hammel Bach

https://www.jstor.org/stable/41640029?seq=1#page_scan_tab_contents

This quotation is not related to Bach, but you might consider it too:

Basso continuo realization can vary from simple harmonization to extensive explorations of harmony and counterpoint. A “full accompaniment” may require as many notes as the fingers can accommodate, and in such cases the rules forbidding consecutive fifths and the like are waived, except as they apply to the two outside (bottom and top) parts.

https://www.britannica.com/art/basso-continuo