Board Thread:Versus Debates/@comment-26958911-20151010214426/@comment-25122992-20160102161515

There's no guarantee it'd surprise Itachi. He's a genjutsu speciallist, after all, thus he must know about different types of it, sound genjutsu including. And Tauya's sound genjutsu Kabuto used has an instant effect after being activated, of cource, he had no time to react. But I doubt he couldn't disperse it without Sasuke's help, it was just the simplest and easiest way to do this back then.