1) The word "school" contains two vowels: O and O.

2) The concept of proportional representation, used in some electoral systems, aims to ensure that political parties' representation in government aligns more closely with the proportion of votes they receive from the electorate.

3) The musical "The Phantom of the Opera" has been running in London's West End since 1986, making it the longest-running musical in history.

4) The oldest known musical instrument is a flute made from a bird bone, estimated to be around 43,000 years old.