A secondary development, in music, is a section that appears in certain musical movements written in 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...

. The secondary development resembles a development section in its musical texture, but is shorter and occurs as a kind of excursion within 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...

 section.

Charles Rosen

Charles Rosen

Charles Rosen is an American pianist and author on music.-Life and career:In his youth he studied piano with Moriz Rosenthal. Rosenthal, born in 1862, had been a student of Franz Liszt...

, who has written extensively on the concept, presents the idea as follows:

The Secondary Development section appears in the great majority of late eighteenth century works soon after the beginning of the recapitulation and often with the second phrase. Sometimes it is only a few bars long, sometimes very extensive indeed. The purpose of this section is to lower harmonic tension without sacrificing interest: it introduces an allusion to the subdominant

Subdominant

In music, the subdominant is the technical name for the fourth tonal degree of the diatonic scale. It is so called because it is the same distance "below" the tonic as the dominant is above the tonic - in other words, the tonic is the dominant of the subdominant. It is also the note immediately...

 or to the related "flat" keys.

The significance of the use of subdominant or similar harmony is related to Rosen's general views on sonata form, in which 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....

 section creates a sense of musical tension by moving to the dominant key (which lies upward from the home key by one on the circle of fifths

Circle of fifths

In music theory, the circle of fifths shows the relationships among the 12 tones of the chromatic scale, their corresponding key signatures, and the associated major and minor keys...

). This tension which is "resolved" in the recapitulation by the return to the tonic. The use of the subdominant in secondary developments, a downward move from the tonic on the circle, provides a sort of balance. As Rosen says, "it is the restoration of harmonic equilibrium as well as the need for variation that gives the Secondary Development its function."

Sometimes the secondary development serves a rather mechanical structural function. In a recapitulation, the musical material that was laid out in the exposition is restated so as to occur entirely (or almost so) in the main key. Thus some kind of alteration is needed to keep the music in the original key, at the spot that corresponds to the place in the exposition where the music changed key. Many secondary developments are placed where they can serve this function. Rosen emphasizes, however, that facilitating the arrangement of keys is not the only or even primary function of a secondary development. As evidence he notes that "the Secondary Development as often as not returns to one of the themes of the first group, which necessitates a still further change later in the section in order to bring the second group into the tonic." As an example Rosen cites Beethoven's "Waldstein" sonata

Piano Sonata No. 21 (Beethoven)

The Piano Sonata No. 21 in C major, Op. 53, also known as the Waldstein, is considered to be one of Beethoven's greatest piano sonatas, as well as one of the three particularly notable sonatas of his middle period . The sonata was completed in the summer of 1804...

, op. 53.

The secondary development sometimes forms a passage of great drama, even the dramatic climax of the movement. For one such instance, see Rosen's discussion of the secondary development in the opening movement of Haydn

Joseph Haydn

Franz Joseph Haydn , known as Joseph Haydn , was an Austrian composer, one of the most prolific and prominent composers of the Classical period. He is often called the "Father of the Symphony" and "Father of the String Quartet" because of his important contributions to these forms...

's string quartet in B minor, Op. 33 no. 1.