The oboe traditionally gives the tuning note A before an orchestral concert.
Orchestral musicians tune to a reference pitch, usually A above middle C, written as A4. The oboe is commonly assigned this task because its tone is clear, penetrating and comparatively easy for a large ensemble to hear. Once the oboe sounds the note, other players adjust their instruments to match it.
The exact reference frequency can vary. Many modern orchestras use A4 at 440 hertz, while some historically informed performances and ensembles use other pitches. The tuning note is therefore not an exclusive property of the oboe, but the oboe is the traditional orchestral source.
The instrument’s double reed gives it a focused sound that carries effectively through an orchestra. Its exposed role also means that the oboist must produce a stable pitch before the rest of the ensemble tunes.