Why Can Parallel Chords Move Without Traditional Resolution?

In traditional tonal harmony, individual voices usually have their own destinations: a leading note rises, a seventh falls, and one chord connects to the next through voice-leading. Parallel harmony instead shifts an entire chord shape to new pitches while broadly retaining its internal intervals, rather like one block of sound moving along the keyboard. It therefore need not be heard each time as a dominant that must resolve to a tonic.

In Debussy's La cathédrale engloutie, fourths, fifths and massive chords rise and fall in parallel motion at the opening and the climax. What matters is not a chain of chords breaking old prohibitions, but a recurring sonorous outline drawing closer. Bass movement, expanding register, dynamics and repetition make imagined bells and an organ emerge from a distance. Functional harmony is weakened, yet direction remains.

This does not mean that every voice loses significance. Debussy moves between exact and diatonic parallelism and uses pedals, pitch collections and formal returns to stabilise the piece. Parallel motion changes how a chord is understood: it becomes a timbral, melodic unit rather than a grammatical station that must always receive a functional label.

On the piano, striking each chord as an isolated vertical object makes the passage heavy. A better approach is to hear the common trajectory of the whole sonority, then balance the top line, bass and inner mass. Pedal can connect resonance, but it should not erase the boundary between chord changes. Colour remains free only when its motion stays clear.

Sources: https://imslp.org/wiki/Pr%C3%A9ludes%2C_Livre_1%2C_CD_125_%28Debussy%2C_Claude%29
https://www.teoria.com/en/articles/2021/debussy-preludes/10/index.php
https://www.jaimeoliver.pe/nyu-analysis