

I feel your pain.....
Years ago, My girlfriend came by to drop off an anniversary card for my parents. When she found No-one home, she went down the driveway and slid it into the outer weatherstrip of the drivers door window on My dads FORD...
I assumed it just blew away, because we never found it, But about six weeks later, Dad Started complaining of Hearing the "LONE RANGER THEME" every time he Rolled down the window.
Next time it happens....Try and locate the area where the sound comes from.
To the best of my Knowledge, There is Nothing about the car itself that would SING Christmas tunes for you.