Literally meaning “continuous bass”, basso continuo was an integral feature of music and ensembles during the Baroque period of the 17th and 18th Centuries. Within the wider ensemble, a small group of players – the basso continuo (often referred to as just “continuo”) parts – would provide the harmonic framework of the piece by playing a bass line and an accompanying chordal progression.
In this article we’ll take a closer look at the use of basso continuo, and at how continuo groups improvised by using an unusual system of musical notation, as well as listening to some beautiful pieces which utilise continuo parts from the Baroque era and beyond.
Continuo parts were generally not written for a specific instrumental lineup, so the exact instrumentation used in performance would depend on what was available to the ensemble in question.
This is in contrast to more recent classical music, which tends to be written for specific instruments.
However, the continuo needs to have at least one instrument capable of playing chords, such as a harpsichord, organ, lute or harp. (Pianos did not become widely used until later).
We also need one or more low-register instruments to provide a bass line.
This might be a cello, bass viol, double bass or bassoon.
The continuo would form part of an orchestra, which would often be directed from the harpsichord, but would be also used in smaller chamber music settings and in opera and choral music.
This large ensemble performance uses a continuo comprising double bass, bassoon, harpsichord and lute:
Meanwhile, this piece by Jean Philippe Rameau sees a solo bassoon accompanied by a two-part continuo of just harpsichord and cello:
Function of the Continuo
Most Western music is centred around moving harmony with a strong bass line.
This is true of most classical music, pop and jazz.
In basso continuo the bass line is written out exactly, while the chordal instrument (or instruments) improvise an accompanying harmony part based upon the implied underlying chord progression.
In tandem, these two parts provide the foundation and harmonic framework of the ensemble, as well as the rhythmic pulse.
In many ways, this is comparable to the rhythm section in pop or jazz groups, where the pianist or guitarist is likely to be told which chords to play at a given time, but not exactly how to play them.
In contrast to this, in most later forms of classical music all of the players are told exactly which notes and rhythms to play all of the time.
Another function of the continuo is to flesh out the sound of the ensemble.
Baroque instruments were not yet fully developed, so string instruments from that time in particular sound rather quiet and thin in comparison to their modern equivalents.
The continuo parts add depth and volume to the ensemble texture.
With its distinctive, twanging sound, the harpsichord can often be heard cutting through the rest of the ensemble.
The chordal instrument has a number of options to choose from in terms of the accompaniment they provide.
They might play ‘block’ chords or more of an arpeggiated chordal texture, perhaps with the inclusion of some typical Baroque ornaments.
While the bass part would have been written out (or realised) exactly using standard notation, the chordal instruments would improvise, at least to some extent, using a notation called figured bass (also sometimes referred to as thoroughbass).
The chordal instruments read from the same part as the bass instruments, and use the bass notes, in combination with some small numbers written below the stave, to work out which chord they are supposed to play.
Figured bass, therefore, is a kind of musical shorthand for written harmony.
It might look something like this:
The numbers written beneath the stave refer to the intervals in the chord that should go above the bass note.
In combination with knowledge of the piece’s key signature and harmonic context, we can work out what the chord is supposed to be.
For example, if we saw the numbers 3-5 (stacked vertically, with the 5 on top – the numbers read highest to lowest, from top to bottom) beneath a C, that would tell us that we have a C major chord in root position (i.e. with the tonic as the bass note).
This is because the intervals in this chord, in relation to the root, are a third (C to E) and a fifth (C to G).
That said, a triad in root position would often have no numeric symbol beneath it at all, because it would be obvious to an experienced continuo player that, unless they were told otherwise, a C in the bass line would mean a C major triad if we were in the key of C major, for instance.
6-3 below the stave implies a chord in first inversion, so with the third in the bass.
So if we see 6-3 below an E in the bass line, this suggests a C major chord in first in version, because the intervals in the chord in relation to the bass note are a sixth (E to C) and a third (E to G).
6-3 chords are usually just written with a number 6, like so:
All of this comes down to harmonic context.
For example, if we saw a 6 below an F in the bass whilst in the key of D flat major, we would recognise that as the tonic chord in first inversion.
But if we saw the same note with the same chord figure whilst in the key of C major, we would recognise it as a D minor chord in first inversion (like the one we see above), because there are no flats in the key of C major.
6-4 refers to a chord in second inversion, with the fifth in the bass.
The four refers to the interval between the bass note and the root, while the six refers to the interval between the bass note and the third of the chord.
There are other, more complex notations that might be used.
A 7 below the stave, for example, refers to a chord with a seventh, while others might have a sharp, flat or natural sign to refer to a note in the chord that lies outside of the key signature.
An excellent understanding of harmony and appropriate musical style is required to play using this notation.
Baroque counterpoint had strict rules about voice leading and intervals.
For example, parallel fifths and parallel octaves were considered ugly, so it was up to the player to make sure that the improvised harmony part adhered to these conventions, even though they would not typically be stated in the part.
Almost all Western music used continuo parts during the Baroque era, which lasted approximately from 1600-1750.
One text that was extremely influential was Del sonare sopra ’l basso (“On Playing upon the Thoroughbass”), a kind of continuo and figured bass instruction manual from the early 17th Century by the Italian composer Agostino Agazzari.
Continuo was used across a broad range of styles and, because the exact instrumentation was flexible, a particular piece might sound completely different when interpreted by different ensembles.
Here is a sonata for flute, violin and continuo by J.S. Bach, one of the most well-known Baroque composers:
In the Classical period that followed (approximately 1750-1820), continuo parts started to fall out of favour.
However, they were still used occasionally, particularly in religious choral music.
C.P.E Bach, the son of J.S. Bach, wrote instrumental pieces featuring continuo well into the Classical era, while Mozart’s operas often make use of a small continuo group during the half-spoken recitative parts:
During the Romantic period continuo was rarely used, although a few composers did write continuo parts for organ as part of large-scale choral works.
One such example is Bruckner’s Requiem in D Minor:
With figured bass falling out of fashion, most modern performances of Baroque pieces have tended to have fully written out parts added in to make them more accessible to the modern player.
However, recent years have seen a rise in authentic period performance practice, so there is a growing number of players today who are able to improvise continuo from figured bass parts authentically.
So, that concludes our look at basso continuo.
We’ve looked at how players would be expected to improvise an accompaniment part using figured bass, and at the history of continuo during the Baroque period and beyond.
Thanks for reading!