Voice Leading with Seventh Chords in Inversion

A root-position V7 can move to a root-position I because the bass just drops a fifth or jumps up a fourth. Invert that V7 and the bass is no longer the root: it's the third, fifth, or seventh of the chord, and each of those tones has its own voice-leading habit. The third and fifth can often hold or move by step depending on the voicing, but the seventh is the strict one. Wherever the chordal seventh sits, it must resolve down by step, and since it's in the bass, that stepwise motion writes the bass line of the next chord for you.

V6/5 has the third of V7 in the bass, which is the leading tone, so it still pulls up by step to tonic, keeping the following I in root position. V4/3 has the fifth in the bass, free to resolve to tonic's root or stay, but the seventh, now in an upper voice, still falls by step. V4/2 has the chordal seventh itself in the bass, and that note resolves down by step straight into the next chord's bass, forcing tonic into first inversion, written I6, because the bass landed on the third of tonic, not the root.

This is why inversion of a seventh chord is never just decoration: it locks in the bass motion of the resolution, which in turn locks in the inversion of the chord that follows. Once you can predict the next bass note from the inversion symbol alone, reading a figured-bass progression gets much faster, and this logic carries straight into the cadences and sequences built from these same seventh chords.