Had some issues with sound after changing to a different 4.4 ROM. Could only get sound from music\streaming apps (probably all apps) when all was minimised and as soon as the screen locked or in an app (even the one where the sound was supposed to be originating from), all sound would go dead.
Tried a few different ROMs with similar results. Would work fine upon first installation, then after a short time would break.
Seems my problem was using the old PA GApps package. As there hadn't been any updates for a long time I hadn't downloaded the latest version. The problem seems to occur when you start pulling/installing updates to google packages.
There might well be other strange behaviour, but this was the main issue I came aware of.
All issues seem to be cured now! So this is an informative post rather than a question. Hope it helps someone out there!