What is Third Inversion?

Third inversion is a chord position that occurs in four-note chords, such as seventh chords, when the seventh of the chord is the lowest note. In this arrangement, the notes of the chord are reordered so that the seventh appears in the bass while the root, third, and fifth are placed above it. Because the bass note changes, the overall sound and harmonic function of the chord can shift.

For example, a C7 chord contains the notes C, E, G, and B♭. In root position, C is the lowest note. In first inversion, E is the lowest note. In second inversion, G is the lowest note. In third inversion, the seventh (B♭) becomes the lowest note, with C, E, and G above it. This may be written as C7/B♭, indicating the seventh chord with B♭ in the bass.

Third inversion chords are often used to create strong tension that leads to resolution in a chord progression. Because the seventh of the chord tends to resolve downward in harmony, placing it in the bass can create a sense of movement toward the next chord. This inversion is commonly found in classical harmony and jazz progressions where smooth voice leading is important.