What is…Basso Continuo?

Stephen Johnson gets to grips with classical music's technical terms

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A basso continuo is, in 17th- and 18th- century music, the bass line and keyboard part that provide a harmonic framework for a piece of music.

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Basso Continuo literally means ‘continuous bass’, or to use the old English version, ‘through bass’. And that, in essence, is what it is.

It’s a feature of Western musical harmony that it thinks from the bottom up. Baroque operas, Beethoven symphonies, jazz improvisations and rock numbers – all would be impossible without a strong, supportive, but also dynamic bass line. 

This is very different from, say, Indian devotional ragas, where music of great polyphonic sophistication unfolds above an absolutely fixed drone. That sense of rootedness is essential to ragas, where the aim is to calm the volatile drama of individual emotional experience.

But in Western classical music, fluid psychological drama has grown increasingly important. Harmony is no longer fixed: it goes on a journey, away from and back to the home chord – the tonic triad. This new, active bass line is the foundation of this movement.

Chords are built up from it, and the notes of each chord are understood as dissonance or consonant in relation to that bass. It is the foundation intellectually, and also emotionally. Without it, things fall apart.

And in the Baroque era in particular that was also true practically. In performance, the bass line would be provided, or at least reinforced, by low instruments such as cello, bassoon or violone. But more important for the ensemble would be the addition of an instrument that could play full harmonies: organ, lute, guitar or harpsichord.

Normally this player wouldn’t have a part written out in full: he’d pay from a bass line, above which were ‘figures’, indicating dissonances or unexpected harmonic turns. The fact that the actual notes weren’t fixed meant that this continuo player could adapt the flow of the chords to fit ornamentations or other improvised elements introduced by the melody instruments. 

This ‘continuo’ player would also be the one who defined the beat. Even at the end of the 18th century, Haydn was still providing this function at the keyboard in performances of his symphonies.

Nowadays, when listening to a Mozart piano concerto, we expect to wait for the soloist to enter; but figures above the bass line in Mozart’s manuscripts suggest that he would have expected to play along with the orchestra even during non-solo passages. So, technically no need for a conductor at all…!

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This article was first published in the September 2013 issue of BBC Music Magazine