If you play a C major chord on a piano and then play an F major chord, you've made a harmonic decision. But classical composers would ask a more specific question: which note in the C chord moved to which note in the F chord, and did it move in a way that makes sense for a voice?
This way of thinking about harmony — as the result of independent voices moving through space — is called counterpoint, and it's the structural foundation of Western classical music from the Renaissance through the late Romantic period.
What a voice is
In counterpoint, a 'voice' is a melodic line that moves independently through a piece. In a four-part chorale (the standard teaching form, developed from church music), the four voices are soprano (highest), alto, tenor, and bass. Each voice has its own range, its own directional preferences, and its own rules about how it can move.
The rules exist not as arbitrary constraints but as formalised observations about what sounds good when multiple voices move simultaneously. They were codified by theorists from Josquin to Fux to Schoenberg, each generation refining and contesting them.
The three types of motion
When two voices move simultaneously, they can move in one of three relationships:
Similar motion: both voices move in the same direction, but by different intervals. Generally acceptable, especially in inner voices.
Contrary motion: the voices move in opposite directions. This is considered the most independent and is preferred in classical counterpoint because it maximises voice independence.
Parallel motion: the voices move in the same direction by the same interval. This is where the famous prohibition appears: parallel fifths and parallel octaves are avoided because they cause the two voices to temporarily lose their independence — they sound like one doubled voice rather than two separate ones.
Why parallel fifths were avoided
The prohibition on parallel fifths (two voices moving in parallel a fifth apart) developed from a specific acoustic property: a perfect fifth is such a strong consonance that when two voices move in parallel fifths, they merge perceptually into one doubled melody rather than two independent lines. The texture collapses from four voices to three.
Bach almost never writes parallel fifths. Beethoven almost never writes them. When Debussy began writing them deliberately in the 1890s, it was a declaration that he was working outside the classical voice-leading tradition — using the 'error' as a colour.
The resolution of the leading tone
One of the most characteristic classical voice-leading rules: the leading tone (the seventh scale degree — B in C major, the note a half-step below the tonic) almost always resolves upward to the tonic. This is because the leading tone creates a sense of incompleteness, of tension aimed precisely at one target. In jazz, the leading tone can go anywhere. In classical harmony, it goes home.
In Mowjera's classical pieces
@chamber_ensemble's collection demonstrates classical voice-leading in the string voicings: each bar sustains a complete triad (root, third, fifth), and from bar to bar, the individual voices move by step where possible. In Spring Prelude, the string chord moves D–A–G–D; note that the top voice (A3 → A3 → B2...) stays on A through the first two bars — oblique motion, one of the safest options in voice-leading. The bass, meanwhile, moves root-to-root: D2 → A2 → G2 → D2, which is allowed because bass motion by larger intervals is conventional.
Counterpoint is the invisible architecture under every bar of classical music. Once you hear it, you understand why the music moves the way it does.