In the novelization of '2001' the monolith had apparitions coming out of it, so if Kubrick had followed suit, whenever it 'spoke' to the ape men, it would have looked something like the ending to Raiders Of The Lost Ark.
I seem to remember Clarke's description in the book was of things resembling revolving wheels appearing out of the monolith, or some such description. That opens up a whole can of worms because it would seem to mimic the Vision Of Ezekiel, and that has had connotations with space men up until, oh, quite recently.
