Soundminer wrote: ↑
Fri Jul 07, 2017 3:20 pm
yes! pulled upwards!!..only After pushed down and into the guitar and only possible because of the side way pressure of the string on the finger!
You can push in or pull up on a string for preparation and get a good sound.....as long as you pluck out and away from the guitar using the downward or upward pressure from the string.
I am sorry but this is simply incorrect (as far as I understand what you are saying), and Mark's description is correct. Several ways to show you this, including data from actual image captures from ultra-high speed cameras showing string displacement.
However, there is also basic physics to consider. You can't "pull" something which already wants to go in that same direction (unless we are playing redefinition games). Pulling (and pushing) a string only makes sense when you are overcoming its resistance; in your stated case, the string already has a restoring force toward its equilibrium (i.e. away from soundboard) which then it will overshoot and thus result in free, decaying oscillation generally in the "up-down" direction; the string is pushing your
finger in that direction while you hold the string in its displaced position (and you are pushing it in the opposite direction into the soundboard, not away from it).
Additionally, as I mentioned elsewhere previously, the actual fingertip-string interaction involves (1) string displacement generally into soundboard, (2) string rolling around itself (and thus travelling a bit toward your fingertip) until static friction is overcome(*)
, (3) string slipping around fingertip/nail, (4) free oscillation (which is like a narrow ellipse trajectory in the frame of the graph below as it has mostly cross- but some along-soundboard component).
This is why what really happens is that at the point of release (at the end of (3)) the string is at its greatest displacement in into-soundboard direction (and there is some displacement in parallel-to-soundboard direction - less for rest stroke and more for free stroke). After that the only force acting on it is the restoring force from being displaced. There is no "pull" up by your fingertip; there is a push up by the string on your fingertip - if you let you fingertip stay there as at the end of (1).
You and especially "guit-box" seem to ignore or be unaware of (2) and (3) so I regularly see the argument about PIP and DIP joint chiefly working to pluck/release based on the supposed inability of the string to go through your finger if you push into soundboard and a bit toward bass string by finger rotation from MCP joint. The flaw in this argument is your incorrect assumptions about the components/phases and physics of the fingertip-string interaction.
Here is a graph of typical experimental data of string cross-section position collected with high speed motion capture equipment. Negative displacement y means into the soundboard; positive x is parallel to soundboard toward bass strings; so this is like looking, from the nut toward the bridge, at a cross-section where (0,0) is where the string cross-section's position is at rest. Note this is not the trajectory of the fingertip; that would be different after phase (1); nor is it the movement of the string relative to finger.
The dots are drawn at equal time intervals which is why the free oscillation phase only has a few compared to the previous phases, as well as why the dots are sparser in the slipping phase compared to the initial displacement and the rolling phase.
The red arrow points to the moment of release. That point does not have to be that close to x=0, but it will be closer to x=0 for rest stroke compared to free stroke, which is where the concept of "shallower angle" for release for free stroke comes from. (The angle formed by the release point-to-(0,0) line and the line of y=0.)
The reason slippage eventually occurs after the string rolls around itself (twists around itself) is as follows:
First, note that the way the string is pushed into the soundboard and the curve of the finger's cross section combine to result in a force component of the string tension in the direction, along your finger's surface, toward the tip/nail/end. In phase (1), static friction is enough to overcome this, and so the string is simply displaced but not moving in relation to the finger which is pushing it "down".
At some point, the displacement is large enough that the tension has increased to the point where there is enough torque to twist the string; the string starts rolling around itself (twists along its length). At this point the strings rolls on the finger's surface toward its tip but is not slipping. This is the rolling phase (2).
Next, as it twists more and more, the combination of torsion and tension components in the direction along the finger surface overcome friction and the string starts slipping along the contour of the finger(tip) until it runs out of contour. This is the end of phase (3) where the release happens.
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