What does oblique motion refer to in counterpoint?

Oblique motion in counterpoint refers to the concept where one voice remains stationary while the other moves either upwards or downwards. This technique is significant as it creates a contrast between the melodic lines and helps maintain the harmonic relationship while enhancing the textural richness of the counterpoint. The stationary voice serves as an anchor, allowing the moving voice to explore different pitches without losing the connection to the harmonic foundation.

The other options highlight different aspects of musical motion that do not align with the specific definition of oblique motion: simultaneous motion depicts two voices moving together in the same direction, which is a separate concept; unlimited harmonic progression pertains to the fluid movement between chords and does not specifically indicate how individual voices relate to one another; and the creation of dissonance through motion focuses on how voices interact in tension rather than the static and moving relationship described by oblique motion.