When the Saints Go Marching In began as a traditional American spiritual and became one of the defining songs of New Orleans jazz, with brass bands playing it at parades, funerals and celebrations for generations. Louis Armstrong's famous 1938 recording helped turn it into a worldwide jazz standard, and its simple, hopeful melody made it easy for audiences everywhere to recognise and sing along. It later became closely linked with sporting celebrations and marching bands, which is why it still appears in films, adverts and online edits as shorthand for triumph and good spirits.