Amarok won't play songs, keeps skipping to the next
Some say install install phonon-backend-xine
but it was already installed automatically, obviously that's not the problem or solution.

Settings -> Configure Amarok
Playback: Configure Phonon
Audio Output: Music

It should show your different audio interfaces, choose Pulse Audio and move it to the top of the list, do the Apply, OK and manually quit Amarok (remember to close it from the tray if it's there).

It still doesn't work, now Phonon when started is saying "it claims it cannot play MP3 files".

Solution:

After installing "libxine1-ffmpeg" it was finally good.