After nearly 5 days of trying every permutation imaginable. 5DAYS!!!!! I have FINALLY managed to get Sonos to “find” and add my iTunes music folder. It is on a Synology NAS drive.
The Pathname I entered was exactly:
//my Synology’s IP address/name of folder in there containing iTunes library
The username and password were the ones for the Synology drive itself and NOT the one for the DS app Synology Assistant.
Good luck to anyone struggling with this nightmare.
You state “The username and password were the ones for the Synology drive itself and NOT the one for the DS app Synology Assistant.” Was this your only problem? It does not seem to be Sonos-related then.
Is it nog logical to you'd the NAS password to gain access to the NAS.
No. Not nearly my only problem. The other 5 days were spent trying to work out all of the computer settings go set and unset, permissions needed, naming conventions, etc. giving up on trying to get it to connect to the library when it was on an external Toshiba hard disk, creating another library and folder in the Synology, fixing its permissions etc etc.
all of this may be a walk in the park to tech geeks, I get that. But for customers without a PhD in Computer Science who just wants good speakers to play all of their music through via their computer, I’d say it’s all a bit much. Here’s an idea. If this is all just standard expectation stuff, let’s have Sonos add that to all of their advertising materials. Should be easy and hey, a new dawn in corporate transparency and customer communication 
Sonos had an easier way to the library but that was deemed to be unsafe. The way they do it now is the normal way to give access to a computer or NAS on a network. Yes, it might look like it's a bit convoluted, but that's Apple or Microsoft or Synology for you.
Sonos does publish a guide for this: Add your music library to Sonos | Sonos What could Sonos do to better explain this?
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