The Stranger Things theme was composed by Kyle Dixon and Michael Stein of the synth band S U R V I V E. The theme plays over the show's title sequence, as well as the credits of most chapters. The version heard in the title sequence was released as the track 'Stranger Things', as part of Stranger Things, Volume One. An extended version is also featured in Stranger Things, Volume Two.
'Stranger Things' is built around a C major arpeggio, played on a bass synthesiser.
Dixon and Stein experimented with "a bunch of ideas" for potential themes, sending over demos to the Duffer Brothers. The Duffers became interested in one demo in particular for its upbeat yet mysterious feel, and asked Dixon and Stein to develop it further.
Dixon and Stein worked on 30 seconds, 45 seconds and 1 minute versions of the track, implementing a sense of build-up and climax. The minute-long version would go on to be played during the title sequence.