Unofficial national anthems: a lot of countries have them.
I grew up in the UK, where the official national anthem is God Save the Queen (which no one likes) but should be Rule Britannia, Land of Hope and Glory or even Jerusalem.
Australia’s national anthem is Advance Australia Fair, but should be Waltzing Mathilda.
The USA has been lumbered with The Star Spangled Banner, where it should be America the Beautiful, Hail Columbia, God Bless America or pretty much anything else that doesn’t require such a ridiculously high range in order to be able to sing it.
Even China, which you wouldn’t expect to be big on alternative national symbols, has a variety of B-side options (Ai Wo Zhonghua, The East is Red) that are all much more fun to belt out than the official tune (March of the Volunteers).
It’s not universal, however. France got it right first time, and as nothing could possibly beat the Marseillaise, has no need for an unofficial anthem.
Singapore, on the other hand, falls firmly in the former camp. The official national anthem is Majulah Singapura, which no one can remember the words to. The unofficial team song, however, is Home, which everyone knows and which has, over time, begun to edge out Majulah Singapura even at official occasions.
In any case, above is a shared rendition of the tune featuring ordinary Singaporean citizens in celebration of Singapore’s upcoming 50th birthday. Enjoy.