HORATIO: Tush, tush, ’twill not appear.
Lacking a time machine, there’s no way for us to determine the original pronunciation of Horatio’s contemptuous non-verbal reply, “tush.” It’s clearly an analogue of our modern “tsk,” and if you drop out the “u” altogether, it even makes a similar sound. The safest pronunciation is probably with a short u, to rhyme with “brush.” If you lengthen the u sound, even so much as a smidgen (to rhyme with “bush”), then you’re into the Giggle Zone.
Modern directors of Shakespeare don’t worry as much as they ought to about the Giggle Zone — a phenomenon in which adolescent audience members (the bread and butter of most companies producing Shakespeare) find a vulgar echo in some otherwise harmless word or phrase, resulting in transgressive giggles from the students, and chastising shushes from their chaperones. It is not the same effect as when Shakespeare actually intends a vulgar gag, because I’d argue that students are smart enough to know when they are being given license to laugh at something juvenile, as opposed to claiming a laugh at the expense of the play’s meaning. Are you laughing with Shakespeare, or at him? Are you giving the script your respect — well played, Shakespeare — or are you dissing it?
Unfortunately, some of these Giggle Zone lines come at the worst possible moments, utterly dissolving any dramatic tension that a scene has rightly earned. My personal unfavourite comes in the final scene of Othello, when Lodovico sees the “tragic loading of this bed” — ie. the bodies of Desdemona and Emilia, momentarily joined by Othello himself, who has just impaled himself. His utterance is only three words long: “O bloody period!” It literally means, “what a horrific end to this story!” but good luck sneaking it past an audience of teenagers without an explosion of laughter. I’ve directed Othello twice, and cut the line both times.
Horatio’s line is not so crucially situated, but it’s still going to provoke the Giggle Zone if it sounds like the actor is talking about his backside. It would be relatively easy to cut it, except I think it’s an important statement of Horatio’s skepticism, precisely because it is so plainspoken. There is no way for an audience to misinterpret his meaning or his attitude — unless, of course, they cannot hear the words because they’re laughing too hard.
An easy fix, though: either coach the actor to pronounce the two “tushes” so that they do not evoke potty humour, or else change “tush” to “tsk,” or some other non-verbal sound that indicates disbelief.