The "CanonGuitar.sgt" playing when the playlist is blank and music is "on" is apparently a "design feature", or, as we used to call them when I worked with a software house - an "undocumented non-feature".
I once had a vendor tell me that their buggy software was "working as coded".
That was before "Doh!" became a catchphrase, but I'm sure I said something similar.