String length behind the nut and behind fretted notes adds a small amount of resonance because they are still mechanically connected via the neck. Any fingertapper knows just how much resonance the strings behind the fretted note add. You can hear this more clearly with acoustic guitars. Try putting a capo on, strum a chord and then dampen the speaking length of the strings and listen to the sympathetic resonance that persists from behind the capo. It's subtle, but it's there. Play the strings behind the capo or nut and you'll hear them faintly through the pickup.
There is a tonal difference between open notes and fretted, we tend to like and use this without realizing it (big chords fretted high up the neck with an open drone string or two anyone?). It doesn't stand out as clearly as you might expect though (unlike the tonal differences between treble and bass on a nylon string), because every note on the neck has a different tonality anyway (thanks to scale length, differing string gauges, distance from the neck joint, etc.). Zero frets reduce the differences, but introduce potential tuning issues.
Saddle is more important than nut when talking upgrades - especially with a UST pickup.
makepeace wrote:
i don't think that there is a lot of difference in density (which is the main factor with regards to transfer of energy in this case) of a good hard piece of bone, and a piece of metal.
There is. Metal also adds a lot of friction, while bone (at least unbleached bone) is self-lubricating.
