I am currently developing two third party skills. One for remote control of some iGeek BT lamps and the other one for voice controlled music playback with mopidy and mpc.
install mopidy from here: https://docs.mopidy.com/en/latest/installation/debian/
install mopidy-youtube with: sudo pip install Mopidy-YouTube and needed stuff with sudo apt-get install gstreamer1.0-plugins-bad
install mpc with: sudo apt install mpc