Music Theory Resources
The term sonata can refer either to an individual piece of music of either one movement or several or to one movement of a multi-movement piece, usually the first movement. It is often referred to as sonata allegro, because of the tempo marking frequently given at the opening of the movement.
Sonata form, also sometimes called first-movement form, since sonata form is typically the form of the first movement of a sonata, derives from the rounded binary form. Like the rounded binary form, it is in two large parts, which in the Classical era are divided from each other by double bars and repeat signs. (These outer manifestations of the original binary nature of sonata form are often discarded in the Romantic and later eras.) However, within those two large parts are three sections--the Exposition, the Development, and the Recapitulation. The Exposition takes up the entire first part of the sonata form, and the Development and Recapitulation take up the second part of the sonata form. In terms of key, the exposition moves from the tonic key to a new secondary key in which it ends, and the development ultimately moves away from this secondary key and then strives to return to the tonic key, which is accomplished at the beginning of the recapitulation, where it remains in the tonic key. If the tonic key is major, the most common secondary key is that of the dominant (V). If the tonic key is minor, the most common secondary key is that of the relative major (III).
The exposition of the sonata "exposes" the main themes and the basic key conflict that constitutes the heart of the sonata. It contains four sections: the Primary Theme (P), the Transition (T), the Secondary Theme (S), and the Closing Theme (K). The primary theme presents the main theme of the movement. It is in the tonic key, and often is constructed so as to reinforce the tonic key. In Classical-era sonatas, the primary theme is periodic in its phrase structure, balanced and proportionate. It will generally end with an authentic cadence. In other words, it is fairly closed. Beginning with Beethoven, primary themes may be outwardly proportionate, but not periodic, and often will end with a half cadence. In such cases, the theme will remain open, and will require closure at some later point in the music.
The transition is the section that modulates to the new key--dominant if begun with a major key, relative major if begun with a minor key. It very often will begin with material from P and in fact might sound like a continuation of P. However, as soon as the tonal digressions begin, the listener knows that this is the transition. This section can end in several ways--with an authentic cadence in the new key, with a half cadence in the new key, or with an elided authentic cadence in the new key, the final chord of which overlaps with the beginning of the secondary theme. There is no periodicity associated with the transition, since it carries modulatory and linking functions. However, there will be phrase regularity and continuity of ideas. The transition does not begin just at the point of modulation, but before that, at or after a strong point of articulation such as a cadence.
The secondary theme announces the arrival of the new key with a theme that is generally contrasting in mood and character to the primary theme (thus reinforcing the inherent difference between the tonic and the new key). With this theme periodicity is usually regained, and it will generally end with an authentic cadence in the new key.
The closing theme continues in the new key and serves to reinforce it through regular functional progressions and often numerous cadences. Regularity of phrasing but not periodicity is a hallmark of the closing theme. There will generally be one cadence that is stronger than any others, and this will serve as the final cadence of the exposition. However, a short phrase or two after this main cadence--a codetta of sorts--may occur. Or there may be another transition section that takes the listener into the development or back to the exposition.
The development is a more free section than the exposition; in it the composer "works out" or "develops" the themes of the exposition. This is done in a myriad of ways. A list would include modulation, sequence, motivic segmentation and extraction, textural changes, etc., that is, any way in which the material from the exposition could be altered or expanded and still remain recognizable. It is a very unstable section; keys are moved through quickly or only hinted at, for example. There is no set harmony pattern or key scheme in the development. However, in spite of this instablity and the overall tenuous nature of the development, it is clearly organized, and can be reduced to just a few sections, from two to four. This sectioning is based on which themes are being utilized and/or the key structure. Since there are only four possible themes from the exposition (although they could be broken up into smaller fragments and therefore increased in number), there generally are no more than four large sections in a development. In fact, there are probably only three themes from the exposition, since the transition is usually based on the primary theme. Sometimes the composer will work through all three and sometimes he/she will pick on just one or two themes, or portions thereof. And sometimes the composer will introduce entirely new material in the development.
Another more stable aspect of the development that occurs often is the incorporation of a goal key. Such a key is reached towards the end of the exposition, before the preparation for the return of the main key in conjunction with the primary theme (the recapitulation). Sometimes a theme is stated in this key, or the composer clearly reaches a half cadence in that key. It will be a key with a subdominant function in relation to the tonic key, as are most of the keys in the development section. This subdominant emphasis throughout the development clearly leads the listener to expect the dominant key, which comes in at the point called the Retransition, the final section of the development that constitutes the preparation for the recapitulation. The retransition is usually in the tonic key but on the dominant harmony, or it could be in the dominant key.
A typical development, then, might look like this: It begins with a section devoted to the primary theme, possibly starting in the dominant and then quickly moving away. A second section could be devoted to the secondary theme, and incorporate into it the motion towards and achievement of the goal key. Or this second section could contain new material in connection with the attainment of the goal key. The third section would be the retransition, with the emphasis on the dominant harmony (or viio7 as a substitute) and on thematic material that would lead back to the primary theme.
After the turmoil of the development, the recapitulation returns both the primary and secondary themes to the tonic key. It restates the primary theme as at the beginning, restates part or all of the transition but with no true modulation (sometimes a "fake" modulation is incorporated here, to give a sense of going away and then returning), and returns the secondary theme and the closing theme to the tonic key. Generally only the transition is changed, but sometimes the closing theme can be somewhat altered, in order to give it a heightened sense of closure, since it is the section with which the sonata usually ends.
In later and longer sonata movements, sometimes there is a Coda, which is necessitated by previous non-closure. For example, if the primary theme in both the exposition and the recapitulation ends only with a half cadence, further closure is required. If the secondary theme is restated in a key other than the tonic (and this can happen in cases in which an unusual key--not the dominant or relative major--is chosen for the secondary key), it will need to be restated in the tonic in the coda. If the thematic periodicity of the primary or secondary theme is missing, then this can also be provided in the coda. (See instruction sheet entitled CLOSURE for more on this.) Many writers and analysts call the coda a second development section. This is not entirely accurate. The coda exists because the composer chose not to provide complete closure in the recapitulation. Why would he/she do this? Well, if the primary theme ends with a half cadence in the exposition, it is more than likely that it will end with a half cadence in the recapitulation as well. Such an exact restatement of the primary theme in the recapitulation is expected, in which case the only appropriate place for additional closure is in the coda. Or a composer may have chosen an unusual key for the secondary theme in the exposition. Then, in the recapitulation, this secondary theme is restated in the key that would be tonic for the original new key in the exposition. This maintains the original dominant-tonic key relationship between the two statements of the secondary theme of sonata form as it developed in the pre-classical and classical eras. If, for example, Beethoven chose the key of D major for the secondary theme in a sonata for which the tonic key was Bb major, then he would restate that theme in the recapitulation in G major, which is the tonic for which D major is the dominant. This preserves the idea of sonata form, even though the initial key relationship between the primary and secondary themes has been expanded to include non-dominant keys, in this case the major mediant. Then, he would need to restate the secondary theme in Bb major in the coda for closure to be attained.
The usual key scheme of the sonata form, then, will be something like this: ||: Exposition : ||: Development : ||: Recapitulation : || P T S K I? II? III? Retrans. P T S K maj: I I-V V V ? ? ? (V) I I I I min: i i-III III III ? ? ? (V) i i i i