1. Locking the joint
This is about a temporary immobilization a member’s joint (example: the forearm and the arm or the finger’s neighboring phalanges) that is connected in a precise position. This locking of the joints can be muscular or ligamental.
Muscular locking creates a resistance in the heart of the joint through an increase in muscle tension. This is a dynamic occurrence and thus requires a lot of the pianist’s energy. It is possible to dose the level of this locking to produce different dynamics and tone qualities.
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Contrary to muscular attaching, ligamental locking is static, and consequently requires much less effort. It means finding a position for the hand through which each preceding bone pushes the following one. By doing this, one forms a chain of lockings, which goes from the shoulder all the way to the bottom of the key (The Neuhaus’ bridge). The major portion of the force needed to strike a key comes then primarily from the force of gravity (i.e. from the falling weight of the Motor Apparatus) and from the shoulder muscles and from the hips (whose muscles push the mass of the torso into movement). The unique role of the weaker muscles of the hands and fingers is to manage this force when striking the keys.
2. Attaching the joint
Simply put, this is about a very weak locking . I have borrowed this very appropriate term from Cz. Sielużycki (►Bibliography) who uses it to refer to...
Attaching is used regularly in advanced pianistic technique, and most particularly in throwing movements, as a support for locking and to prevent the negative effects of inertia.