Unison

Harmony; agreement; concord; union.

Identity in pitch; coincidence of sounds proceeding from an equality in the number of vibrations made in a given time by two or more sonorous bodies. Parts played or sung in octaves are also said to be in unison, or in octaves.

A single, unvaried.

Sounding alone.

Sounded alike in pitch; unisonant; unisonous; as, unison passages, in which two or more parts unite in coincident sound.

occurring together or simultaneously; "the two spoke in unison"