Thanks to guitarrista and his excellent post and graph I can now formulate a (hopefully) final description on how to 'handle' the string to get a free oscillating sound, i. e., a projecting sound.Which if you ask me is the only standard for correct tone production. The rest is totally based on taste and preference.
So it's important to make a distinction between taste and preference...timbre, volume ect. vs the free oscillating projecting sound on it's own.
I am talking about the latter because if one does not have the skill to produce a sound with that quality first and foremost..well, let's just say that's like trying to build a house with bricks of jello instead of cement. Nobody will enter that house without fearing getting yuckie stuff in their ears.
Ok, sorry for that ridiculous analogy...but it's hard to describe you know.
It's also important to note that this is for people who are NOT satisfied with their tone or (mostly beginning) students who can't seem to get a grip on getting a good one.
It's a matter of days, weeks...months maybe, before these people, students give up...understandably so (nobody likes jello in their ear). It doesn't have to be like this with a better description which involves not only what the finger is doing but also what the string should be doing. This is what is overlooked most of the time in guitar pedagogy in my opinion.
There are two sides to every story and it's amazing how people can put one and one together if you give them the right description. But you have to decribe both sides as best you can. That's your first job as a teacher, to start with the abc's ....so here goes.
step 1. make contact and push straight down without letting the string roll around itself
step 2. Pluck/strike/play/swipe the string by changing direction, keep in contact with the string while doing this and feel IT rolling around itself
until it slips free, slides over the fingertip/pick and starts vibrating freely
The start of the rolling part is very crucial
1. contact and displacement - No rolling of the string!!
2. play - rolling of the string until it starts to slip and slide on it's own
If one starts the rolling process during step one...which is what most beginners do, due to lack of control and muscle tension...
The string will find it's maximum rolling capacity ( it can't roll no more ) before or during step two.
We DO NOT want this because when this happens...the finger get's stuck to the string and vice versa
..and a jerking motion is required to get loose..
The sound that comes from this is very unpleasant. In fact if you slow this sound down with some software (slowdowner!), the beginning of the sound when released with this unavoidable (if step 1 is done wrong) jerking motion.....sounds like a window slamming in the wind....bam bam bam !!! this is followed by a sound that is very invasive and unpleasant...like a loud carhorn. It sounds Forced...which is exactly what it is. It has no build up, no swelling and no change in volume from onset to loudest point
This is because the string can't slide and the 'overrolled' state of the string (tension overload) comes back during the release (jerk) and the string starts rolling back. But, while it does...it bounces up and down against the fingertip!!! leaking all the energy that would have been 'sounded' if the string would have slipped and slided on it's own. This results in a non-free oscillating sound....an obstructed sound.
I don't care what anyone says....Nobody likes this sound..it's not music and never pleasant to the ear.
In comparison, the onset of the sound when part 1 and 2 is done correctly sounds like a wave rolling in on the beach...wuuushhhhhh
This rolling wave is then followed by a clear and pleasant sound that swells up to it's loudest point where it really starts to sing...it has build up and all kind of harmonics within itself.
Kind of Heavenly in fact...music
The hard part for the beginner is really part 1. If done right part 2 sorts itself out mostly....But if part 1 gets ingrained in the muscle memory the wrong way....that's the end for the aspiring guitarplayer! This is why the 'pendulum motion' description is not helpfull at all if you ask me. In fact, the opposite.
So..as teachers, I say hammer that point home first. Then proceed with the fun part..how to make music with this skill. Rythm , chords , melodies, timbre, timing, volume ect ect ect.