You need to add spotify ppa repository in order to install 64 bits version:
# nano /etc/apt/sources.list.d/spotify.list
add this ppa:
deb http://repository.spotify.com stable non-free
# apt-key adv –keyserver keyserver.ubuntu.com –recv-keys 94558F59
# apt-get update
# apt-get install spotify-client
Run spotify-client