Just to follow up to myself, at least you're not asking about the time signature of the theme tune from The Terminator. Not even the composer can answer that very well--the rhythm came from a tape loop that he really liked, but it wasn't exactly in sync with any kind of kind of planned rhythm or anything--the sounds in the tape loop just made a cool-sounding backdrop for the rest of the tune. 13/16 is the closest approximation that anyone has, ever come up with for the purposes of making an orchestral score, but really, it's just a tape-loop-based oddity. (1980s) technology strikes again! It was a happy accident (as Bob Ross would put it), the composer liked how his tape loop sounded, plastered more music on top of it, and when he was happy with what he had, moved on, cashed his paycheck, and forgot about it. So when John Williams contacted him years later asking him about it, he was just as confused as John Williams was.