Yesterday, I'd tried and failed to build the Phonon Music Player example project; the error was "cannot find lphonon". A quick Google led to my creating a symbolic link from a phonon library in /usr/lib; I had libphonon.so.4, but it was presumably looking for libphonon.so, so I did sudo ln -s /usr/lib/libphonon.so.4 /usr/lib/libphonon.so, and was then able to build the project and listen to audio files successfully.