Secondary development
A secondary development, in music, is a section that appears in certain musical movements written in sonata form. The secondary development resembles a development section in its musical texture, but is shorter and occurs as a kind of excursion within the recapitulation section. Charles Rosen, 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 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 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). 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