Connective tissue is ubiquitous, you can't escape it. Fascia in particular weaves its way through the body embedded in muscles and lining bones and internal organs. Sheets of superficial fascia lie just beneath the skin, continuous with the web of deep fascia internal to it. Every time we move, and we're always moving, this fascia is under tension, transmitting forces from one part of the body to another. Here we will examine more closely the sequence of events that gets a sound out of you guitar.
Proprioceptors in your muscles inform your brain exactly where your hands and fingers are. Given that information your motor cortex initiates a firing sequence to take you from your current position to the guitar, let's just look at fretting one note for now. An elctro-chemical signal reaches your arm and generates contraction in the finger flexors and corresponding lengthening of the extensors along with contraction of muscles that stabilise the wrist.
Muscle fibres, each surrounded by a layer of fascia, are arranged roughly parallel with each other so that they all pull in the same direction. The fascial layers typically converge at the tendon at end of each muscle where the combined force of all the contracting muscle fibres is exerted at its attachment to the bone. The bone, itself comprised of connective tissue, is also encased in layers of fascia. The connective tissue from the muscle tendon effectively continues on until it covers the bone. Likewise the fascia surrounding the bone is embedded with the joint capsule providing yet another physical connection, this time to another bone.
So as the finger flexors contract tension is generated in the associated fascia which pulls on the inside of the phalanx (the bone in the finger). Because the extensors have relaxed tension on the opposite side of the finger is reduced and the bone moves around a pivot at the joint until the finger hits the fretboard. At this point touch and pressure sensors tell the brain that now would be a good time to reduce the contraction until there is just enough to keep the finger on the string.
So this simple movement creates tension in the fascia of the hand and the forearm. This fascia remember is not only in the tendons but throughout the muscle, lining the bones and in the joints as well. This isn't a problem when this tension is dissipated through movement but when it isn't, or when the fascia is overused, there will be consequences throughout the musculo-skeletal complex.