Fundamental bass
Rameau's imagined sequence of chord roots (basse fondamentale).
What it means
The fundamental bass, French “basse fondamentale,” is an idea of the French composer and theorist Jean-Philippe Rameau. It means the imagined sequence of the roots of the chords of a piece, regardless of which note actually sounds in the bass. All inversions of a chord thus belong to the same root.
Musical use
Rameau developed the idea in his Traité de l'harmonie of 1722. He used it to explain the relationship of chords and the coherence of a harmonic progression from the root instead of the often changing bass note. The fundamental bass is regarded as a basis of modern chord theory and of scale-degree theory, in which chords are named after their root on the degrees of the scale.
The fundamental bass should be distinguished from the figured bass, the really played bass line with figured chords, and from the basso seguente, which simply accompanies the lowest voice of the texture. The fundamental bass is not a played voice but a theoretical model.
Performance practice
When analysing a piece, determine the root of each chord regardless of inversion and write the sequence down: this shows the actual harmonic movement. Practise this on simple chorales until recognising roots comes naturally.