3.7 How identity shapes form  (Page 2/3)

Rather than ignoring or overlooking these idiosyncrasies, Mozart amplifies them in the rest of the movement. For instance, when the second theme is first played, it is symmetric:

However, when it is immediately repeated, Mozart adds an extension .

A transition typically separates the first and second themes in an exposition. In Symphony No. 40 , the transition is rather short:

In the recapitulation, Mozart could have easily reused this transition by reworking it slightly. However, instead of a “routine” transition, Mozart more than doubles its length, offering some of the most dynamic music of the entire piece.

Just as there are extensions throughout the movement, so there are elisions . For instance, in the development sections, the lower strings “step on the toes” of the upper ones by entering sooner than expected.

In a typical Sonata Form, the recapitulation is a great moment of affirmation: Stability is emphatically restored with the return of the tonic.

In this piece, the boundary between the development and the recapitulation is not so clear. Instead, the development and recapitulation overlap: Once again, the theme anticipates its accompaniment; as a result, the crucial tonic harmony does not arrive until the theme has already started.

Thus, the asymmetry of Mozart’s theme has deformed the anticipated behavior of the form. Rather than being perfectly balanced, the form resists equilibrium: It is twisted into surprising shapes by the elisions and extensions.

Mozart’s piece makes such a strong impact because of the depth of commitment to its material. Long before life coaches, music such as this has been telling us: “Be true to yourself.”

We now turn our attention to an unusual fugue . Like a canon, a fugue is based on melodic imitation . However, in a canon , one voice leads and the others follow from beginning to end. In a fugue , the lead changes hands.

In traditional terminology, the sections where the complete theme—called the fugue subject -- is stated are called expositions ; these are rooted in a specific key. The sections where the lead changes hands —and the music changes keys--are called episodes .

The opening exposition generally stays in the tonic key until all of the voices have entered. This establishes the “home key,” from which the music then departs and to which it eventually returns.

The fugue subject —is typically drawn from the Major or minor scales. Often, the keys of the expositions are chosen so that, taken as a whole, the sum of the fugue statements adds up to the notes of the scale from which the subject is drawn. Thus, in a fugue in C-Major, the sum total of all the statements will reproduce the C-Major scale (or at least come close).

So far, we have described the design of a traditional fugue. The first movement of Bela Bartok’s Music for Strings, Percussion and Celeste departs from the standard model.

Bartok’s subject is not based on the Major or minor scales. Instead, it is chromatic —that is, the notes are pressed closely together, with no open spaces. In Listen , Joseph Kerman describes the theme as “tentative, circuitous and troubled.”