Codetta
The purpose of this is to bring the exposition section to a close with a perfect cadence in
the same key as the second group. Often the codetta contains a sequence of themes each
of which arrives at a perfect cadence. The whole of the exposition may then be repeated.
The last bar of the exposition is often slightly different between the repeats, the first one
pointing back to the tonic where the exposition began and the second one pointing
towards the development.
Development
The development generally starts in the same key as the exposition ended and may move
through many different keys during its course. It will usually consist of one or more
themes from the exposition, altered and occasionally juxtaposed, and may include new
material or themes. Alterations may include taking material through distant keys,
breaking down of themes and sequencing of motifs.
The development varies greatly in length from piece to piece. Sometimes it is relatively
short compared to the exposition, as in the case of the first movement of Mozart’s ‘Eine
kleine Nachtmusik’ K 525 and of his piano sonata in G major. In other cases it is quite
long and detailed as in the first movement of Beethoven’s ‘Eroica’ symphony. It nearly
always shows a great deal of tonal, harmonic and rhythmic instability than the other
sections. At the end the music will turn towards the home key and enter the
recapitulation. The transition from the development to the recapitulation is a crucial
moment in the piece.
Recapitulation
The recapitulation is an altered repeat of the exposition.
First subject group
This is normally given prominence as the highlight of a recapitulation. It is usually in
exactly the same key and form as in the exposition.
Transition
This is now altered so that it does not change key but remains in the piece’s home key.
Second subject group and codetta
These are usually in roughly the same form as in the exposition, but are now in the home
key which sometimes involves transformation from major to minor, or vice versa, as
occurs in the first movement of Mozart’s symphony no. 40 K 550. More often, however,
the second subject group may be recast in the tonic major of the home key, for example C