Now commonly accepted as the point of reference for musicians in the Western world, A 440 hertz only became the standard pitch during an international conference held in 1939. The adoption of this norm was the result of decades of negotiations between countries, involving a diverse group of performers, composers, diplomats, physicists, and sound engineers. Although there is widespread awareness of the variability of musical pitches over time, as attested by the use of lower frequencies to perform early music repertoires, no study has fully explained the invention of our current concert pitch. In this book, Fanny Gribenski draws on a rich variety of previously unexplored archival sources and a unique combination of musicological perspectives, transnational history, and science studies to tell the unknown story of how A 440 became the global norm. Tuning the World demonstrates the aesthetic, scientific, industrial, and political contingencies underlying the construction of one of the most "natural" objects of contemporary musical performance and shows how this century-old effort was ultimately determined by the influence of a few powerful nations.