Chord inversion

What it means

A chord keeps its identity no matter which of its notes lies at the bottom. The inversion consists in transferring the lowest note an octave upward, so that the next higher chord note moves into the bass. The triad C–E–G thus becomes E–G–C and after that G–C–E. In function-theoretical terms nothing changes: all three remain the tonic (I) in C major. What changes is the harmonic firmness and what the bass does melodically. What is decisive is solely the lowest sounding note, not the order of the upper voices.

In the notation

The inversions bear names after the intervals standing above the bass. For the triad: root position (root in the bass), the six-three chord with the third in the bass, the six-four chord with the fifth in the bass. For the seventh chord a fourth possibility is added — the six-five chord (third in the bass), the four-three chord (fifth in the bass), the two chord (seventh in the bass). In degree notation the figures appear as an addition to the roman numeral; in figured-bass figuring they stand directly under the bass note, often shortened: 6 means the six-three chord, 6/4 the six-four chord.

Musical use

Inversions allow a bass voice that steps rather than leaps. A succession T–Sp–S–D sounds ponderous with nothing but root positions; if individual chords are inverted, a continuous line arises, and the harmonies join smoothly. Each inversion has its own weight in this. The root position is stable and capable of closing, the six-three chord lighter and pressing forward; the six-four chord counts as needing resolution and typically does not stand freely but as a suspension before the dominant or as a passing chord. The closing chord of a perfect cadence therefore stands almost always in root position.

The chord inversion is to be distinguished from the interval inversion: there a two-note interval is turned over and changes its name (a third becomes a sixth), while here the chord stays the same and changes only its position. Likewise to be distinguished from the inversion is the slash chord, in which the bass note is expressly prescribed and may also be foreign to the chord.

Performance practice

Practise inversions not as theoretical knowledge but at the instrument: play a triad in all three positions in succession and hear how its weight shifts. When accompanying, the rule of thumb is to choose the position that lies closest to the previous one — so the fingers move little and the texture sounds calm. When harmonising, take care not to use the six-four chord casually; it calls for a continuation.