Sonic Pi is an open-source music creation and performance tool. It was initially developed as a postdoc research project to help introduce and teach programming concepts in schools but has since grown into a powerful musical instrument used by live-coding DJs in nightclubs and music festivals. In this talk we’ll explore some of the key technical innovations that power Sonic Pi such as deterministic randomisation and its concurrency model which supports live-hotswapping of code and the precise manipulation of time. We’ll examine how functional programming techniques have both been a major influence and are a critical part of the future - from its roots in Clojure to its future on the BEAM. Expect plenty of live coding, beats, basslines and synth riffs and to leave the talk inspired to use your programming skills to become the DJ of the future.