Back in the 1800s, a clock tower was built in Cambridge, England as part of University Church. (Yeah, that'd mean it was part of Cambridge University. This isn't rocket science.) The chimes that were installed there played a little ditty based loosely on a symphony/hymn by George Frideric Handel called "I Know That My Redeemer Liveth," although the words and music were later arranged by a guy named William Crotch. (And you thought high school was rough for YOU.) The words went something like this:
Lord through this hour,
Be Thou our guide
So, by Thy power
No foot shall slide.
These notes were selected by the general contractors who set up Big Ben and the surrounding clock tower. They really dug how they sounded in Cambridge, and thought that song should be used for the main jingle before each hour's time was struck. They weren't the only ones who liked it -- chances are you've heard the same song played on a clocktower or grandfather clock more times in your life than you can count.
Next time you hear these notes (mi-do-re-so), you'll be able to impress your friends and colleagues with some trivia about where they're from and what they're called: the Westminster Chimes.