Which of the following terms describes motion where one voice remains stationary while another moves?

The term that describes motion where one voice remains stationary while another moves is oblique motion. In this context, one voice, or part, maintains a single pitch while another voice moves to create harmonic movement or progression. This technique is often used to create texture and support in music, allowing for the establishment of a stable tonal center against which the moving voice can create interest and tension.

In contrast to oblique motion, parallel motion would involve both voices moving together in the same direction at the same interval, which does not align with the description provided in the question. Contrary motion involves both voices moving in opposite directions, which also differs from the scenario of one voice being stationary. Lastly, pedal point motion involves sustaining a single pitch (the pedal point) while other voices move around it, but it is typically associated with a specific bass note or chord rather than the general case of one voice being stationary. Therefore, oblique motion clearly encapsulates the idea of one voice remaining still while another is in motion.