Unison

Unison is the term for multiple voices or instruments playing exactly the same pitch — or the same pitch class across multiple octaves (octave unison). The Italian unisono (or its abbreviation unis.) is the corresponding performance direction.

Unison playing produces a particular powerful effect. With multiple performers on the same line, the resulting sound has greater body and force than a single voice — the famous unison opening of the Marseillaise, the unison string passages of Beethoven and Brahms, the unison brass calls of Wagner — all derive their power from the combined force of multiple voices on a single line.

The direction unisono (‘in unison’) cancels divisi or harmony, instructing all section members to play the same line. The opposite is divisi (split into multiple parts).

Latin, ‘one sound’ — unus (‘one’) + sonus (‘sound’).

Match exactly with your section. Pitch, articulation, and dynamics must be identical. Any deviation creates ‘chorusing’ — a slightly out-of-tune effect — that weakens the unison’s power.