Root position and inversions · Triads · Music theory
What decides the position of a chord is its lowest note, the bass. With the root in the bass it is in root position; with the 3rd, in first inversion; with…
Root position and inversions
What decides the position of a chord is its lowest note, the bass. With the root in the bass it is in root position; with the 3rd, in first inversion; with the 5th, in second inversion.
The figures give the intervals above the bass. Root position has no figure (it would be 5/3); first inversion is figured 6 (I⁶) and second inversion, 6/4 (I⁶₄).
What changes when inverting
First inversion lightens the chord: it keeps its function but with a more mobile bass, and allows stepwise bass lines. Second inversion is another matter: it has a 4th above the bass, so it is treated as unstable, appearing only in very specific uses: cadential, passing and neighboring.
The most important is the cadential one. According to Piston, the tonic six-four before V works as a double appoggiatura over the root of the dominant: C and E fall to B and D over a bass that does not move. So although it has the notes of I, its function is dominant.