$ wget -q -O - https://apt.mopidy.com/mopidy.gpg | sudo apt-key add - 
$ wget -q -O /etc/apt/sources.list.d/mopidy.list https://apt.mopidy.com/stretch.list 
$ sudo apt-get update 
$ sudo apt-get install libspotify12 libspotify-dev libportaudio