As you attemt the development exercises you may find that for some invisible reason your tongue, jaw, larynx or whatever you are working on just keeps on going 'wrong' and won't do what you want it to.
The problem is that the majority of the parts of the upper vocal tract are all connected to the brain by a shared nerve. This means that it takes some additional time to develop isolation. Here's an illustration:
Try this: Place the fingertips of your non-dominant hand (usually the left) flat on a table top, with you palm 2 to 3 centimetres from the table, making a kind of spider form. Now with the first two fingers (nearest the thumb) set up a rhythmic one-two-one-two walking-type action, (8th notes at 160 bpm if you are a musician) . This should be relatively easy to do. Now use the remaining two fingers and do the same, three-four-three-four. You may find this a whole lot harder to do. Piano players and guitarists may find it not so hard as they have already practised this a lot.
This is hard to do because there are only four nerves to the fingers. Fingers 3 and 4 share a nerve, as they normally operate together when grasping. The brain has to learn to especially code the signals in that shared nerve in order for the hand to differentiate commands addressed at each of the fingers in question.
So it is with jaw, back of tongue, vocal cords, and the muscles that control the larynx height. When any of the affected parts moves, others will tend to move too. One of the objectives of doing the exercises in the prescribed manner is to achieve isolation between vocal tract parts.
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