Which composition by Karlheinz Stockhausen is cited as the first true quadraphonic composition?

*Kontakte* (1960).

The quadraphonic era in spatial audio development saw significant contributions from Karlheinz Stockhausen. His 1960 work, *Kontakte*, is frequently recognized and cited within the history of spatial sound as being the first composition that truly implemented the principles of quadraphony. This involved utilizing four distinct speaker positions arranged strategically around the listening area, typically designated as Front, Left, Right, and Back channels. Stockhausen continued pushing boundaries, later deploying an even larger array of 55 loudspeakers arranged spherically for the Osaka Expo in 1970, demonstrating continued exploration beyond the foundational four-channel setup.