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In its most general aspect, counterpoint involves the writing of musical lines that sound very different and move independently from each other but sound harmonious when played simultaneously. In each era, contrapuntally organized music writing has been subject to rules, sometimes strict. By definition, chords occur when multiple notes sound simultaneously; however, harmonic, "vertical" features are considered secondary and almost incidental when counterpoint is the predominant textural element. Counterpoint focuses on melodic interaction—only secondarily on the harmonies produced by that interaction. In the words of John Rahn:

It is hard to write a beautiful song. It is harder to write several individually beautiful songs that, when sung simultaneously, sound as a more beautiful polyphonic whole. The internal structures that create each of the voices separately must contribute to the emergent structure of the polyphony, which in turn must reinforce and comment on the structures of the individual voices. The way that is accomplished in detail is...'counterpoint'.[1]

The separation of harmony and counterpoint is not absolute. It is impossible to write simultaneous lines without producing harmony, and impossible to write harmony without linear activity. The composer who chooses to ignore one aspect in favour of the other still must face the fact that the listener cannot simply turn off harmonic or linear hearing at will; thus the composer risks creating annoying distractions unintendedly. Bach's counterpoint—often considered the most profound synthesis of the two dimensions ever achieved—is extremely rich harmonically and always clearly directed tonally, while the individual lines remain fascinating.

Ears wrote: Counterpoint has it's roots in the medieval mindset where music was the part of the dancing of the cosmic spheres and where the composers strove for unity and dissonance was handled under strict conditions.