In European classical music, musical development is a process by which a musical idea

Idea

In the most narrow sense, an idea is just whatever is before the mind when one thinks. Very often, ideas are construed as representational images; i.e. images of some object. In other contexts, ideas are taken to be concepts, although abstract concepts do not necessarily appear as images...

 is communicated in the course of a composition

Piece

Piece or pieces may refer to:* A single unit of something* An informative or creative work, such as a work of art, journalism, academic research, etc.** Musical piece, a work of music, sometimes called an opus* Chess piece* Jigsaw puzzle piece...

. It refers to the transformation

Transformation (music)

In music, a transformation consists of any operation or process that may apply to a musical variable in composition, performance, or analysis. Transformations include multiplication, rotation, permutation In music, a transformation consists of any operation or process that may apply to a musical...

 and restatement

Theme (music)

In music, a theme is the material, usually a recognizable melody, upon which part or all of a composition is based.-Characteristics:A theme may be perceivable as a complete musical expression in itself, separate from the work in which it is found . In contrast to an idea or motif, a theme is...

 of initial material, and is often contrasted with musical variation

Variation (music)

In music, variation is a formal technique where material is repeated in an altered form. The changes may involve harmony, melody, counterpoint, rhythm, timbre, orchestration or any combination of these.-Variation form:...

, which is a slightly different means to the same end. Development is carried out upon portions of material treated in many different presentations and combinations at a time, while variation depends upon one type of presentation at a time.

In this process, certain central ideas are repeated in different contexts or in altered form so that the mind of the listener consciously or unconsciously compares the various incarnations of these ideas. Listeners may apprehend a "tension between expected and real results" (see irony

Irony

Irony is a rhetorical device, literary technique, or situation in which there is a sharp incongruity or discordance that goes beyond the simple and evident intention of words or actions...

), which is one "element of surprise" in music. This practice has its roots in counterpoint

Counterpoint

In music, counterpoint is the relationship between two or more voices that are independent in contour and rhythm and are harmonically interdependent . It has been most commonly identified in classical music, developing strongly during the Renaissance and in much of the common practice period,...

, where a theme or subject might create an impression of a pleasing or affective sort, but would go on to further delight the mind as its contrapuntal capabilities are gradually unveiled.

The musical form

Musical form

The term musical form refers to the overall structure or plan of a piece of music, and it describes the layout of a composition as divided into sections...

 which traditionally exploits development to the fullest is the sonata form

Sonata form

Sonata form is a large-scale musical structure used widely since the middle of the 18th century . While it is typically used in the first movement of multi-movement pieces, it is sometimes used in subsequent movements as well—particularly the final movement...

. In this form there is a section after the exposition

Exposition (music)

In musical form and analysis, exposition is the initial presentation of the thematic material of a musical composition, movement, or section. The use of the term generally implies that the material will be developed or varied....

and before the recapitulation

Recapitulation (music)

In music theory, the recapitulation is one of the sections of a movement written in sonata form. The recapitulation occurs after the movement's development section, and typically presents once more the musical themes from the movement's exposition...

which is called the development section, where material from the exposition section is developed. In some older texts the development section of a sonata may be referred to as "free fantasia."