An extended fan-mix of the "Stranger Things" theme song:
The series is an amazing example of tactfully done 80's nostalgia - the pulsing John Carpenter-esk synth score, combined with familiar elements of both horror and kid-adventure Sci-fi from that era: ET, The Goonies, Close Encounters of Third Kind, all wrapped in a Twin Peaks/X-Files-esk show on Netflix. A highly recommend series.
Here's some additional altered versions of the theme song, found on this Nerdist article:
The series was scored by Michael Stein and Kyle Dixon, who were once part of an Austin Texas Synth group called s-u-r-v-i-v-e: