major where the movement is in C minor as in Beethoven’s Symphony no. 5 in C minor
opus 67 and his C minor piano concerto. Key here is more important than mode (major
or minor). The recapitulation provides the needed balance even if the material’s mode is
changed, so long as there is no longer any key conflict.
Coda
After the final cadence of the recapitulation the movement may continue with a coda
which will contain material from the movement proper. Codas, when present, vary
considerably in length but, like introductions, are not part of the ‘argument’ of the work.
The coda will end, however, with a perfect cadence in the home key. Codas may be quite
brief tailpieces or they may be very long and elaborate. Examples from Beethoven are
the finale of his symphony no. 8, the first and fourth movements of his symphony no. 5,
the first movement of his piano sonata in F minor opus 57 ‘Appassionata’ and the final
movements of his ‘Moonlight’ and ‘Tempest’ Sonatas.
Monothematic expositions
The move to the dominant key in the exposition is not always marked by a new theme.
Haydn, in particular, was fond of using the opening, often in a truncated or otherwise
altered form, to announce the move to the dominant. Mozart, despite his prodigious
melodic gift, also occasionally wrote such expositions, for example, in his piano sonata K
570 and his string quintet K 593. Such expositions are called ‘monothematic’, meaning
that one theme serves to establish the opposition between tonic and dominant themes.
This term is misleading since most monothematic works have multiple themes with
additional themes in the second subject group.
Only on occasion, for example, in Haydn’s string quartet opus 50 no. 1, did composers
perform the tour de force of writing a complete sonata form exposition with just one
theme. Charles Rosen’s view is that the crucial element of the classical sonata form is
some sort of dramatisation of the arrival of the dominant and, while using a new theme
was a very common way to achieve this, other resources, such as chamges in texture and
salient cadences, were also accepted practice.
Key of second subject need not be in dominant
The key of the second subject may be other than the dominant, or relative major, or
relative minor. About halfway through his career Beethoven began to experiment with
other tonal relationships between the tonic and the second subject group. Beethoven, as
well as other composers, in these cases used the median or submediant. In the first
movement of the ‘Waldstein’ sonata Beethoven modulates from C major to the mediant
of E major, while in the first movement of the ‘Hammerklavier’ sonata he modulates
from B flat major to the submediant of G major.
Exposition may contain more than two key areas