The principal trombone is considered the leader of the low brass section, while the principal trumpet is generally considered the leader of the entire brass section. While the oboe often provides the tuning note for the orchestra (due to 300-year-old convention), there is generally no designated principal of the woodwind section (though in woodwind ensembles, the flute is often considered the leader.) Instead, each principal confers with the others as equals in the case of musical differences of opinion. Most sections also have an assistant principal (or co-principal or associate principal), or in the case of the first violins, an assistant concertmaster, who often plays a tutti part in addition to replacing the principal in his or her absence.