Contrapuntal composition applies the principles of species counterpoint to create two or more melodically independent voices that are simultaneously harmonically coherent. Beyond strict species exercises, free counterpoint allows greater rhythmic variety and expressive flexibility while maintaining the foundational principles: voice independence, preference for contrary and oblique motion, careful treatment of dissonance, and attention to the contour of each individual line. Imitative counterpoint — where voices enter in succession with the same or transformed material — is the organizing principle behind canons, inventions, and fugues.
Begin by writing strict two-voice first-species counterpoint, then progressively relax the constraints through third and fifth species. Transcribe a Bach two-part invention, annotating where voices exchange material and how dissonances are prepared and resolved.
From your work in species counterpoint, you know the rules that govern how two voices interact: consonant intervals on strong beats, dissonances treated as passing tones or neighbor tones, and a strong preference for contrary and oblique motion to keep the voices feeling independent. Contrapuntal composition takes those rules out of the exercise context and puts them to expressive work. Free counterpoint doesn't abandon those principles — it internalizes them well enough to bend them purposefully. The difference is like moving from writing grammatically correct sentences in a language class to actually writing prose: the grammar doesn't disappear, but it recedes into the background as you focus on meaning.
The organizing principle behind most contrapuntal music is imitation: one voice introduces a melodic idea, and another voice enters with the same or transformed version of it. In a Bach two-part invention, the right hand opens with a short figure, and the left hand answers with it a beat or two later — often at a different pitch level. This creates the sensation of a conversation or a chase between voices. The challenge is that while one voice is stating the theme, the other must provide a compelling countermelody that sounds independent, not like an afterthought. This is where your knowledge of contrary motion pays off most directly: if the theme ascends, the countermelody should descend or hold, creating contrast.
Beyond basic imitation, contrapuntal composers have a toolkit of transformations for developing a theme: inversion (flipping the theme upside-down so ascending intervals become descending), augmentation (stretching it out in longer note values), diminution (compressing it into shorter values), and stretto (overlapping entries before the previous voice has finished). Each transformation keeps the material recognizable while refreshing it. Bach's fugues are masterclasses in how much mileage can be extracted from a single four-bar subject by subjecting it to these operations across many voices and key areas.
The harmonic dimension is what distinguishes contrapuntal writing from mere melodic layering. Each interval choice implies a harmonic context: a third and a fifth above a bass implies a root-position triad; a third and a sixth suggests first inversion. Good two-voice counterpoint creates the convincing illusion of full chords through careful selection of consonant intervals at structurally important moments. Dissonances — prepared by a consonance and resolving stepwise downward — create the tension that makes resolution feel earned. When you study a Bach invention, notice how the dissonances almost always appear as suspensions (a note held over from the previous consonance, clashing with the new harmony below) and resolve predictably. This predictability is what makes the dissonance expressive rather than random.
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