Most often, this is due to a Spotify Connect that hasn’t been cleared. Ok, every time someone has reported this. There has been no other explanations offered. People seem to forget they were on your WiFi and playing something from Spotify on your speakers. When they open back up their Spotify, they think they’re playing locally, but are still connected to your system.

Fortunately, there is an easy way to kill all Spotify Connect connections. Once everyone has finished using your Sonos, just play some non-Spotify stream on your Sonos. This will kill all outside connections, and leave just you connected to your system. If you want, at that point, you can reconnect to Spotify, having broken all Spotify Connect connections. 

Thanks for the suggestion. I’ve cleared the Spotify connections in the past but they return. We do not and have never used Spotify. For various reasons it is highly unlikely anyone other than my family has access to the WiFi network where Sonos runs.

For today at least there was no rogue Spotify stream. I cleared old alarms and paired unused music services yesterday just in case...

The next time, and if, it happens again, submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it. But don’t post the resulting diagnostic number here, they get sensitive about GDPR.

There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution. I suspect it will include where the ‘start’ command came from…although I’m not certain, as I’ve never seen what is in a diagnostic, not being a Sonos employee. 

Happened again this morning. Captured the system diagnostic and waited out a 25 min hold to talk to support. Took ~1 hr for them to conclude “its coming from a Spotify app on your network”--which I’ve said before should not be possible. Further they refused to share the contents of the diagnostic report despite reading back various bits to me and claiming the report supported their conclusion (maybe? was difficult understanding everything that was said and the person seemed to be repeating someone else’s words).

So I did a little digging into my network data (I use Ubiquiti gear which has extensive logging and data collection). I can see that no “foreign devices” were on the Sonos network where Spotify played (so it’s not someone doing a drive-by). I can see the Spotify “app” (aka service) accessed by devices on my network--mostly the Sonos devices that played the music but also my own phone. Checked that my phone does not have the Spotify app installed and my browsing history indicates I have never visited Spotify.com. Unfortunately the Ubiquiti logging does not let me pinpoint when my phone accessed spotify.com (most occurrences have been while everyone is asleep). Maybe the Sonos (S1) app does that for some reason?

For now I blocked the spotify app on my Sonos network. Hopefully I’ll remember when I actually do want to use spotify on this network and it mysteriously fails to work .

I’m more convinced than ever this is a Sonos issue (and rebuilding my Sonos network would not help--unless factory resetting the devices clears some bogus state). Maybe someone has reverse-engineered the diagnostic report format so I can look at my own data (assuming I can get to it--seemed like the app was sending it directly to sonos but I can easily intercept that on my end).

Have you attempted to sign-in to this nonexistent SPOTIFY account? If an account exists, maybe you can change the password. If you can change the password, this should churn up some dust. I don’t know if SONOS support would be willing to share any SPOTIFY account details with you.

Remember, Spotify Connect ‘access’ doesn’t need to come from your phone. Anyone who has access to your local network can set up a Spotify Connect session, and once they leave your WiFi, still have a ‘connection’ through Spotify. I guess a long winded way of saying ‘it may not be you, but someone else’.

I can’t think of any reason at all, if you’ve never installed the Spotify connection in the Sonos app, either S1 or S2, would randomly reach out to Spotify. unless perhaps you’re listening to Sonos Radio? They may use Spotify for some of that content, but I wouldn’t think it would reach out when you’re not using it. 

To my knowledge, no one has ever explained where the Sonos diagnostic is stored in their db, nor attempted to reverse engineer that data. If you’re willing to figure that out, there are lots of us that would be interested. 

The Spotify account identity is unclear. It shows up as “Guest” in the Sonos app (screen shot in my OP) but who knows what it really is (other than Sonos who have my diagnostic report but won’t share the contents). IIUC Sonos devices initiate the TCP connection to Spotify based on some received control msg so they must know at least the local IP address of the client that sent that msg; that would help me figure out what device is initiating all this.

I control who can login to the WiFi network and I can see what devices have logged in and/or connect to the Spotify service. Other than Sonos devices &  my personal phone there was also 1x connection from a Chromecast dongle (which might be legit because there is a Spotify app on the device). The only plausible explanation (other than a hacked device) is this is on Sonos (e.g. an alarm that triggers a Music Service is mistakenly triggering Spotify). But they wouldn’t help.

If I figure anything out about the diagnostic report I’ll post here. It's not a high priority for me unless my traffic rule fails to silence the rogue Spotify music.

Think I’ve resolved this--and (spoiler) it was my fault . I was able to identify the clients initiating the Spotify connections; they were on a Guest network (separate from my Sonos network). I thought this network was isolated--it has it’s own vlan--but I had not configured it isolated so when Spotify Connect probed for available audio devices it found my Sonos speakers. Since I marked the Guest network isolated I’ve seen no unsolicited Spotify Connect requests.

Not a Sonos problem.