This is a fairly high-level, technical presentation. It might seem abstract to someone who has not already seen Melo-rhythm, Melo-Harmony, and Melo-lines.

The Langer Hinge in Melody

Definitions
A Melodic Entity is a phrase, or section, of the Melody, which comes to a full stop
          (like a sentence, a paragraph, a chapter, depending on its length),
     composed of entities in each of its components.
A Melo-rhythmic Entity is a section of the Melo-rhythm which comes to a full stop
     with a Masculine Rhyme.
A Melo-harmonic Entity is a Chord Pattern which comes to a full stop
     with a DOMINANT / TONIC cadence.
A Melo-lines Entity is a section of the Melo-lines, which comes to a full stop
     with the Orbit 1 to Orbit 1 line,
          (possibly the Orbit 2 to Orbit 1 line).
An entity (in any of Melody's components) is fundamentally composed of 2 equal parts,
     first, an Antecedent, which "opens" the entity,
     followed by a Consequent, which "closes" the entity.
The Langer Hinge is the specific element which keeps an Entity "open" (desiring to continue),
          and which is placed at the end of the Antecedent of the Entity, on the Beat of the cell,
     whatever form of Entity is involved.
There will be close relationship between the contents of the Langer Hinge,
          at the end of the Antecedent of the Entity,
     and the contents which close the Entity,
          at the end of the Consequent of the Entity,
               for these two spots are placed at the Off-beat and the Beat of the large Cell of the Entity.

Variety within a Melodic Entity
There will be a specific form of hinge for each component of the Melody.
Since Entities in each of the 3 different components are not necessarily of the same length,
          (it is actually preferable that they not be),
     Langer Hinges, in the middle of the different lengths of Entities,
          will not necessarily coincide, as is evidently preferable.
The different lengths of Entities in the three dimensions of Melody,
          and the staggering of the Langer Hinges,
     will be established as one of the most subtle and delicate aspects of melodic quality.
A Melodic Entity can now also be defined as one where the entities close in each of the three components.

The Langer Hinge in Melo-rhythm

In Melo-rhythm, the Langer Hinge is either -
     a Feminine Rhyme, or
     a Pick-up to the next Cell, or possibly both,
          which keeps the Entity open,
               to be closed, eventually, by the Masculine Rhyme,
                    placed at the end of the Entity.

It is in Melo-rhythm that the presence of the Langer Hinge was first perceived and identified.
     Only quite a bit later was it also discovered in the chord Patterns of Melo-harmony, and
          much later was it definitely considered to be an integral element in the Entities of Melo-lines.

Changing Levels

The Langer Hinge can be of considerable assistance in choosing Level Changes.
     In the Footsies we saw how to handle these Level Changes, aligning them properly.
We will now see how to choose these Level Changes properly,
     where to place the larger and smaller levels.

In an AC entity
Changing from a larger to a smaller level
     has the effect of placing a large pick-up in the center,
               between the Antecedent and the Consequent,
          which acts as a Langer Hinge tying the whole AC together.
     An excellent choice, frequently used.

In an AABA entity
However, in the Bridge of an AABA entity, the situation is completely different.
     Considering the BA as an AC entity, makes the larger-smaller choice very tempting,
          but the large-level relationship between the opening AA and the following BA must not be neglected,
     and the Langer Hinge must be in the center, after the AA, with the Bridge at a smaller level,
          which it usually is, though unfortunately often placed late.

The Langer Hinge in Melo-harmony

In Melo-harmony, the Langer Hinge is fundamentally the DOMINANT chord, which keeps the Entity open,
          though it may be replaced by a variety of possibilities of Tenant Chord,
     to be closed, eventually, by the TONIC chord, more specifically by the DOMINANT / TONIC progression,
          placed at the end of the Entity.

The Langer Hinge in Melo-lines

In Melo-lines, the Langer Hinge is fundamentally Orbit 2 which keeps the Entity open,
     to be closed, eventually, by Orbit 1, usually by the Orbit 1 to Orbit 1 line
               possibly by the Orbit 2 to Orbit 1 line,
          placed at the end of the Entity (see Orbits).

Symmetry

The Langer Hinge seems to provoke a considerable amount of Symmetry
     between the 2 halves of the Entity involved, the Antecedent and the Consequent,
          especially between the first and third quarters of the Entity.

We will constantly be referring to the Langer Hinges concerning this Symmetry,
     in Melo-rhythm, Melo-harmony, and Melo-lines.