Recently I was configuring low-privilege accounts for my kids on the Syno. Soon afterwards I got complaints arriving at the service desk 🙂 because they not unable to render music out to Airplay-enabled devices using Audio Station.
Allowing non-admin user is fairly easy, just start Audio Station, click on Settings on the top menu then click on the tab Privileges. For each user you wish to enable that feature, enable the check box USB/UPnP Render Mode.
This will allow not only replaying to AirPlay but also to directly-connected USB sound devices and other UPnP devices as well if they expose this capability. I accidentally discovered that my new TV screen does UPnP rendering too :).
Note: I am running DSM 4.1 but I suppose it should work on less recent DSM as well.
Happy “Synologying” !