Originally Posted by Victory Pete
The string is still in contact under full tension with the nut along with your finger and string on the fret, What is so mysterious about that?
Well, the mysterious thing is that behind the fret after the string has been fretted the string isn't moving. In fact in many cases it is in contact with other frets on the fret board. If it did vibrate it would setup sympathetic vibrations which would be quite distracting.
How can a string that isn't moving effect way a guitar sounds?