A few weeks ago, libFLAC was updated from 1.1.0 to 1.1.1 as stable. There
was a message at the end to run

revdep-rebuild --soname libFLAC.so.4 and
revdep-rebuild --soname libFLAC++.so.2

since these libraries had been updated.

A few days later, 1.1.1 was marked as ~x86 again, and emerge downgraded
back to 1.1.0. HOWEVER, there was no message about running revdep-rebuild
again.

If you ran the above, you will find that sound is broken and no sound will
come from KDE and other applications that rely on libFLAC since the old
dependencies were wiped out!

I reinstalled the 1.1.1 version again by adding it to package.keywords and
all is right. I suppose one could also run revdep-rebuild to reinstate the
old libraries, but this is lengthy (kdemultimedia is in the group) and
will be undone as soon as 1.1.1 is stable again.

HTH