Background: I have never used Rhythmbox on this computer.
I just accidentally opened Rhythmbox while my MP3 player was plugged in. Without asking me or explaining what it was doing it started "Importing..." with high disk IO activity in my home folder. I exited the program to stop it, but not before it reached about 30% completion.
What did it just do?
Update: It occurred to me that the IO activity I saw on my home folder might just be coincidental, if Rhythmbox defaults to scanning my home folder when it is first run. I found this in its Preferences screen:
Does this help explain what Rhythmbox was doing? If it's relevant, I do not have Music folder in my home folder.