How to get spotify native on slackware.

Navigate to http://repository.spotify.com/pool/non-free/s/spotify/ and download the approriate .deb file for your architecture.

spotify-client-qt_0.6.6.10.gbd39032.58-1_<ARCH>.deb at the time of the writing.

Extract the .deb files using the ar command

ar vx spotify-client-qt_0.6.6.10.gbd39032.58-1_<ARCH>.deb

Now you should have a file called data.tar.gz that contains the files that you need. Extract that

tar zxvf data.tar.gz

Now you should have a folder called usr. cd into that folder and as root, copy the binary and theme files into the approriate places.

cp bin/spotify /usr/bin/
cp -R share/spotify /usr/share

Now you can execute spotify and voilà. It should start

Source: http://gnuwhatimsaying.com/spotify-on-slackware-13-37-linux/