Note to Macbeth, Act 1, Scene 6, opening stage direction: "Hoyboys"
A very persuasive article, 'Ominous Oboes', on the Finding Shakespeare site, argues that this stage direction, "Hoyboys," is one of the first uses of atmospheric music. The author points out that the same stage direction is used twice more in the play: once in the next scene, during which Macbeth commits to killing King Duncan, and again just before the witches summon up the apparition which tells Macbeth that the descendants of Banquo will be kings. In each of these scene there is nothing in the text that explains the sound of the oboes, so it seems that Shakespeare is using the oboes simply to create an ominous tone. This is something the does not appear anywhere else in Shakespeare; in Macbeth and other plays Shakespeare uses sound effects to create storms, and in many other plays he inserts songs and dances, but in no other play is there an unexplained sound.