Sorry, my question wasn't as explicit as I thought it was.
I thought it would be clear that Swan Lake somehow got itself imported on to my iPhone.
The only streaming I ever do is via AirPlay...to my stereo via my AirPort Express Base Station, which I assume isn't involved, and I never sign in to my Apple ID.
I was poking around my iPhone pane, and I did hit "Sync" at some point or other, but I most certainly did not either select or drag anything.
Also, my guess is that the music began playing when the import completed, but I'm pretty sure that I wasn't listening to Swan Lake at the time.