Review: Chord Inversions and Figured Bass

A triad can be arranged with the root, 3^rd, or 5^th of the chord as the lowest note.

A triad with the root as the lowest note is in root position, a triad with  the 3^rd as the lowest note is in first inversion, and a triad with the 5^th as the lowest note is in second inversion.

Figured bass is a useful tool for quickly identifying and building chords. Numbers (“figures”) are written under the chord to indicate the intervals over the lowest note, thereby indicating the inversion of the chord.  The figures used in figured bass are the same as those used in Roman numeral analysis.

a. A chord in root position has the intervals of a 3^rd and a 5^th over the lowest note. A chord is assumed to be in root position, so in the figured bass no numbers are written under the chord.

b. A chord in first inversion has the intervals of a 3^rd and a 6^th over the lowest note. Since the distinguishing characteristic of this chord is that it has a 6^th over the lowest note rather than a 5^th, in the figured bass a “6” is written under the chord.

c. A chord in second inversion has the intervals of a 4^th and a 6^th over the lowest note. When identifying the chord, both the “4” and “6” are written under the chord, with the higher number placed over the lower number.

Note that whether a chord is in root position or in an inversion depends only on the lowest note. The intervals over the lowest note can be in any position.