A method of notating the harmonic and rhythmic structure of a piece of
music, without explicitly writing every note. Figured bass is notated by
writing out a bass line and figures that indicate what kind of chord
to build on top of it. Playing from this notation is called realizing a
figured bass, and is essentially improvisation because the chords that
are indicated can be built in more than one way.
Figured bass was used mainly during the Baroque era (especially by
Bach) for notating continuo, the light ensemble used for accompaniment;
this usually consisted of a keyboard instrument such as harpsichord or
organ and a low string instrument, usually cello or string bass.
However figured bass is also used today in music theory education,
because it provides a convenient notation for studies of harmony, part
writing and voice leading.
As was mentioned before, figured bass is written as a bass line, which
provides the lowest note of the chord and the rhythmic structure. Below each
bass note, there can appear a figure that indicates exactly what kind of
chord should be built on that note. Absence of a figure implies that the
chord is a simple chord of the root, third, and fifth in root position
(meaning the root is in the bass). So a C in the bass with no figures
underneath would indicate that the chord is a C chord, and thus can be
constructed of C, E, and G in no particular order. Note that in realizing a
figured bass, you never introduce accidentals unless they're specifically
indicated.
The following figures are used to indicate the structure of the chord
(stacked vertically in real figured bass, but no way to do that here). In
bold is what is written, followed what it designates in full, followed by a
brief summary:
- 6: 6 3, first inversion
- 6 4: 6 4, second inversion
- 7: 7 5 3, seventh chord in root position
- 6 5: 6 5 3, seventh chord in first inversion
- 4 3: 6 4 3, seventh chord in second inversion
- 2: 6 4 2, seventh chord in third inversion
- 9: 9 7 5 3, ninth chord in first root position
Other combinations of numbers may be written to indicate voice leading. A
number of chromatic alterations can be indicated as well: a sharp next to or
a line through a number indicates that degree is to be raised by one
half-step, and if a sharp is not next to a number, is assumed to mean the third.
Likewise with flats, double sharps or double flats.