The sonata form, also called sonata-allegro form or first movement form, is a musical structure that usually has three main parts: an exposition, a development, and a recapitulation. This form has been widely used since the middle of the 18th century, during the early Classical period.

Although it is most commonly found in the first movement of multi-movement compositions, it is sometimes used in later movements, especially the final one. Teaching sonata form in music theory is based on a standard definition and a set of ideas about why the form has remained popular and varied over time. This definition was developed in the second quarter of the 19th century. Most experts agree that the form has three main parts: an exposition, a development, and a recapitulation. However, the exact details of how these parts work together can vary, making it hard to describe the form with one single model.

The standard definition emphasizes how themes and harmonic patterns are introduced in the exposition, explored and contrasted in the development, and then resolved in the recapitulation. It also notes that an introduction and a coda may appear in some pieces. Each section is often divided further or described based on how it contributes to the overall structure.

After its creation, the sonata form became the most common structure for the first movement of works called "sonata," as well as other long musical pieces like the symphony, concerto, and string quartet. Because of this, there is a large amount of theory about what connects and differentiates the use of sonata form across different time periods. Even pieces that do not follow the standard description of sonata form often have similar structures or can be analyzed as variations of the standard model.

Defining 'sonata form'

Sonata form is considered the most important structure in music from the Classical period through the 20th century, according to the Grove Dictionary of Music and Musicians. This structure is most clearly shown in the first movements of multi-movement compositions, whether performed by an orchestra or a small group of instruments. Because of this, it is often called "first-movement form" or "sonata-allegro form," as the first movement in a typical three- or four-movement piece is usually in a fast tempo called allegro. However, sonata form is not limited to this type of movement. It is also found in other musical styles, such as minuets, concertos, and sonata-rondos. Additionally, it is associated with certain expressive and stylistic features, such as dramatic contrasts, strong energy, and a focus on the emotional development of musical themes, as described by theorists like Donald Tovey.

The Italian word "sonata" can refer to a single-movement instrumental piece, but it is important to distinguish this from "sonata form." The term "sonata" comes from the verb "suonare," meaning "to play," and was used during the Baroque and early 18th centuries to describe many instrumental works that were not structured in sonata form. Later, in the late 18th century, the term "sonata" was commonly used to describe a multi-movement composition with three or four parts. However, this multi-movement structure is different from sonata form, which refers only to the specific structure of a single movement.

The concept of sonata form developed over time and is tied to two historical periods. While the late 18th century, particularly through the works of Joseph Haydn and Wolfgang Amadeus Mozart, is known for its most refined examples of the form, early theories of music composition did not use the term "sonata form." One of the earliest detailed descriptions of the structure was provided by Heinrich Christoph Koch in 1793. Unlike modern explanations, Koch focused on the movement's modulation plan and key changes, rather than the development of musical themes. This suggests that sonata form may have evolved from a simpler structure called binary form.

Today, the model of sonata form taught in music education is more focused on the development of themes. This approach was first clearly outlined by Anton Reicha in 1826, Adolf Bernhard Marx in 1845, and Carl Czerny in 1848. Marx is often credited with coining the term "sonata form." This model was influenced by the study of Ludwig van Beethoven's piano sonatas and emphasizes the contrast and evolution of musical themes within a single movement.

Definition as a formal model

A sonata-allegro movement is divided into sections. Each section has a specific role in the structure of the music.

• It may begin with an introduction, which is usually slower than the main part of the movement.
• The first required section is the exposition. The exposition introduces the main musical ideas for the movement: one or two themes or groups of themes, often in different styles and keys, connected by a transition that changes keys. The exposition usually ends with a closing theme, a short ending called a codetta, or both.
• After the exposition comes the development, where the musical ideas are explored in new ways using different harmonies and textures.
• The development leads back to the recapitulation, where the musical ideas return in the main key. To complete the structure, any material that was not in the main key is played in the main key, either fully or partially.
• The movement may end with a coda, which comes after the final ending of the recapitulation.

The term "sonata form" is a topic of debate among scholars and composers. Its creators suggested that Classical and Romantic composers followed a specific structure. However, today it is used more as a tool for analyzing music rather than a strict rule for composition. While the descriptions here explain many first-movement structures, there are many variations. Scholars like Charles Rosen argue that the term should be plural, "sonata forms," because of these differences.

Some variations include:
• An exposition with only one theme, repeated in different keys, often used by Haydn.
• A third theme group in a different key than the first two, used by Schubert (e.g., in his String Quintet, D. 956) and Bruckner (e.g., in his Symphony No. 4).
• The first theme returning in the subdominant key instead of the main key, as in Mozart’s Piano Sonata No. 16 in C, K. 545 and Schubert’s Symphony No. 5.
• The second theme group returning in a key other than the main key, as in Richard Strauss’s Symphony No. 2.
• A long coda that continues developing musical ideas rather than ending, found in Beethoven’s middle-period works, such as his Symphony No. 3.

During the Romantic period, many composers used variations and changes in structure so often (e.g., Mahler, Elgar, and Sibelius) that the traditional description of "sonata form" is not enough to explain their complex music.

Compared to similar forms from the late Baroque period, sonata form can be identified by three key features:
• A separate development section that includes a transition back to the recapitulation.
• The first theme group and the main key returning at the same time.
• A full or nearly full return of the second theme group in the recapitulation.

Outline of sonata form

The standard description of the sonata form is:

The introduction section may be included or left out. If it is included, it is often slower than the main section and usually focuses on the dominant key. It may or may not include material that appears later in the exposition. The introduction adds weight to the movement, such as in the famous dissonant introduction to Mozart's "Dissonance" Quartet, K. 465. It also allows the composer to begin the exposition with a theme that would be too light on its own, as seen in Haydn's Symphony No. 103 ("The Drumroll") and Beethoven's Quintet for Piano and Winds, Op. 16. The introduction is usually not included when the exposition is repeated, though the Pathétique is an exception. Later, Chopin's Piano Sonata No. 2 (Op. 35) includes the introduction in its repeat.

Sometimes, the introduction's material appears again later in the movement, often in the coda, as in Mozart's String Quintet in D major, K. 593, Haydn's "Drumroll" Symphony, Beethoven's Piano Sonata No. 8 ("Pathétique"), and Schubert's Symphony No. 9 ("Great"). In some cases, it appears earlier, such as at the start of the development in the Pathétique Sonata or at the beginning of the recapitulation in Schubert's Symphony No. 1.

The main themes of the movement are introduced in the exposition. This section can be divided into smaller parts. Most sonata form movements share similar harmonic and thematic patterns, though exceptions occur in some 19th-century and later works. These include:

• First subject group (P) – one or more themes in the tonic key. Most pieces follow this structure, though exceptions exist.
• Transition (T) – the section where the composer moves from the key of the first subject to the key of the second. If the first group is in a major key, the second is usually in the dominant key. If the first group is in a minor key, the second is usually in the relative major.
• Second subject group (S) – one or more themes in a different key (typically the dominant) from the first group. These themes often differ in rhythm or mood from the first group and are often played softly.
• Closing zone (C) – a section after the second subject group that reinforces the new key. It includes new musical material that differs from the second subject group.

The exposition is often repeated, especially in classical and early romantic works, and more frequently in solo or chamber music than in concerti. First and second endings are sometimes used at the end of the exposition. The first ending returns to the tonic key, while the second ending leads to the development.

The development section usually begins in the key where the exposition ended and may move through many different keys. It often includes themes from the exposition, altered or rearranged, and may include new material. The length of the development varies, with shorter examples in Classical-era works like the first movement of Eine kleine Nachtmusik and longer examples in Romantic-era works like the first movement of the Eroica Symphony. Classical-era developments are typically shorter due to a focus on symmetry, while Romantic-era developments are more detailed and expressive. In some late Classical and early Romantic concertos, the development section ends with another exposition, often in the relative minor key.

At the end of the development, the music usually returns to the tonic key to prepare for the recapitulation. In rare cases, it may return to the subdominant key before transitioning back to the tonic. The transition from the development to the recapitulation is crucial. The final part of the development is called the retransition, which prepares for the return of the first subject group in the tonic key.

Exceptions to this pattern include the first movement of Brahms's Piano Sonata No. 1, where the retransition emphasizes the dominant seventh chord on C instead of G, and the fourth movement of Schubert's Symphony No. 9, where the retransition prolongs the dominant chord on G before returning to the tonic key in E♭ major. Another exception occurs when the dominant key is replaced with the dominant of the relative minor key, as in Haydn's String Quartet in E major, Op. 54 No. 3.

Sometimes, the retransition begins with a false recapitulation, where the first theme group's material is played before the development is complete. This creates a surprise when the music continues to modulate toward the tonic key, used for comic or dramatic effect, as in Haydn's String Quartet in G major, Op. 76 No. 1.

The recapitulation is a modified repeat of the exposition and includes:

• First subject group – usually in the same key and form as in the exposition.
• Transition – sometimes includes new material, called a "secondary development."
• Second subject group – usually in the same form as in the exposition but now in the home key. This may involve a change from major to minor or vice versa, as in Mozart's Symphony No. 40 (K. 550). More often, it is restated in the parallel major of the home key, such as C major for a movement in C minor.

Exceptions to the recapitulation structure include works by Mozart and Haydn, where the second subject group may begin the recapitulation if the first subject group was extended in the development. Themes from the second subject group may also be omitted if they were elaborated in a resolving key, as seen in Mozart's Piano Sonata in C minor, K. 457, and Haydn's String Quartet in G major, Op. 77 No. 1.

After the closing cadence, the musical argument is considered complete. If the movement continues, it may include a coda.

The coda is optional in Classical-era works but became essential in many Romantic-era works. It follows the final cadence of the recapitulation and may extend the movement's ending.

Variations on the standard schema

In some musical compositions, the shift to the dominant key in the exposition is not always marked by a new theme. Haydn often reused the opening theme, sometimes shortened or altered, to signal this shift, as seen in the first movement of his Sonata Hob. XVI/49 in E♭ major. Mozart also used this technique in works like his Piano Sonata K. 570 and String Quintet K. 593. These expositions are sometimes called "monothematic," meaning one theme establishes the contrast between the tonic and dominant keys. However, this term can be misleading, as most "monothematic" works actually include additional themes in the second subject group. Rarely, as in the fourth movement of Haydn's String Quartet in B♭ major, Op. 50, No. 1, did composers write a complete sonata exposition using only one theme. A more recent example is Edmund Rubbra's Symphony No. 2.

Charles Rosen notes that the use of a new theme was a common way to highlight the arrival of the dominant key in Classical sonata form. However, other techniques, such as changes in musical texture or strong cadences, were also used.

In some Classical-era sonata-form works, there is no transitional material between the first and second subject groups. Instead, the piece moves directly from the first group to the second using common-tone modulation. This occurs in the first movement of Mozart's Symphony No. 31 and the third movement of his Symphony No. 34, as well as in the first movement of Beethoven's Symphony No. 1. In these cases, the first subject group ends on a half-cadence in the tonic key, and the second subject group immediately follows in the dominant key without a transition.

The key of the second subject may differ from the dominant or relative major, depending on whether the piece is in a major or minor key. For minor-key movements, modulating to the minor dominant was sometimes used, though this often created a bleak or grim effect, as seen in Beethoven's and Mendelssohn's works.

Beethoven also experimented with other tonal relationships between the tonic and the second subject group. During the Romantic era, composers like Beethoven often used the mediant or submediant keys instead of the dominant. For example, the first movement of the "Waldstein" sonata in C major modulates to E major (the mediant), while the "Hammerklavier" sonata in B♭ major modulates to G major (the submediant). Tchaikovsky and Chopin also used these techniques, with Chopin even writing expositions that did not modulate at all.

Beethoven frequently used the submediant major in minor-key sonata-form movements, as seen in Symphony No. 9 and Piano Sonata No. 32. In some cases, the second repeat of the exposition began on the minor dominant and ended on the major mediant. Richard Strauss, Brahms, and others also used the submediant key in their works.

Occasionally, major-mode sonata movements modulated to a minor key for the second subject area, such as the mediant minor or relative minor. In these cases, the second theme often returned in the tonic minor during the recapitulation before shifting back to the major mode.

During the late Romantic period, composers sometimes modulated to distant tonal areas to represent divisions of the octave. For example, Tchaikovsky's Symphony No. 4 modulates from F minor to G♯ minor and then to B major in its first movement. Brahms and Tchaikovsky also used the major dominant key in minor-key sonata forms.

Sonata forms can include more than two key areas. Schubert, for instance, composed sonata forms with three or more key areas, such as in his Quartet in D minor, D. 810 ("Death and the Maiden"), which uses D minor, F major, and A minor. Chopin's Piano Concerto in F minor also uses multiple keys in its exposition. These works often follow specific tonal schemes, such as i–Iii–v or i–Iii–Vi.

The second subject group can begin in a key and then modulate to its parallel major or minor. For example, in Brahms' Symphony No. 1, the second subject group starts in E♭ major and moves to E♭ minor. Similar patterns appear in Beethoven's Piano Sonata No. 8 and Dvořák's Symphony No. 9.

The first subject group is not always entirely in the tonic key. In more complex expositions, brief modulations to distant keys may occur before returning to the tonic. For example, Mozart's String Quintet in C, K. 515, briefly uses C minor and D♭ major within the C major first subject group before moving to D major. Schubert and later composers often used even more complex harmonic progressions, such as in his Piano Sonata in B♭, D. 960, where the theme is presented in multiple keys.

In concerti

An important change in the traditional sonata-allegro form appears in the first movement of the Classical concerto. In this version, the usual "repeated exposition" of the sonata-allegro is replaced by two sections: the "tutti exposition" and the "solo exposition." Typically, the "tutti exposition" does not include the soloist, except in early classical works where the soloist may play a "continuo" role. This section also does not contain the key change that defines the sonata-exposition. The soloist becomes active and participates in the key change to the dominant or relative major only during the "solo exposition." In Mozart's Concerto No. 9, the soloist is heard early, but the opening piano solo or flourishes occur before the proper exposition begins. This structure also appears in works from the Classical-to-Romantic transition, such as Beethoven's Piano Concertos No. 4 and No. 5, and in Romantic concertos, like Grieg's A minor concerto or Brahms' B♭ major concerto.

The unique structure of the concerto allows the solo instrument to "own" certain themes or musical ideas, which are introduced only during the "solo exposition." Mozart often used this technique.

At the end of the recapitulation in a concerto movement with sonata form, a cadenza is typically played by the soloist alone. This section is often improvised (though it may not always be) and serves to extend the harmonic tension on a dominant-quality chord before the orchestra concludes the piece in the tonic key.

Some people argue that the "double exposition" does not exist, claiming that the first subject theme continues from the start of the "tutti exposition" through to the first subject of the "solo exposition," meaning there is only one exposition.

History

The word "sonata" first appeared in the 17th century, a time when instrumental music was beginning to develop separately from vocal music. The term comes from the Italian word "suonare," meaning "to sound on an instrument." It described a piece meant to be played, not sung, and was different from "cantata," which was for singing. At this time, the sonata was often in a binary form, usually with two sections repeated twice (AABB), and sometimes included parts of three-part structures. An early example of a simple pre-Classical sonata is Pergolesi's Trio Sonata No. 3 in G major.

During the Classical era, composers established standard ways to structure the first movements of pieces and the overall layouts of multi-movement works. At first, there was a wide variety of ways to arrange these movements, but over time, these became accepted norms. The practices of composers like Haydn and Mozart, along with others, became highly influential. Their works helped shape how future composers approached the forms they used. As time passed, the study of their music led to a clearer understanding of how to structure the first movement of a piece. The sonata form, as it is now described, is closely linked to the practices of the Classical period. Even before being formally described, this form became central to musical composition, influencing and changing other musical structures. Beethoven's Appassionata sonata is an example of this.

In the Romantic era, the importance of the sonata form was widely accepted. Composers made the form more clearly defined and used it as the foundation for serious concert and chamber music. During the 19th century, debates arose about what "development" and sonata practice truly meant, and how the Classical masters influenced music. It was ironic that, while the form was being made more clearly defined by figures like Czerny, many composers of the time created works that broke some of the established rules of the form.

The sonata form remained important throughout the history of classical music, even into the modern era. In the 20th century, scholars worked to base the theory of the sonata form on fundamental rules of music tones. This period saw an expansion of acceptable practices, leading to the idea of a "sonata principle" or "sonata idea" that could unify works of this type, even if they did not strictly follow the traditional descriptions.

Sonata form and other musical forms

Sonata form has features similar to both binary form and ternary form. In terms of key changes, it is similar to binary form, with the first part moving from the main key to the dominant key and the second part returning to the main key (this is why sonata form is sometimes called compound binary form). In other ways, it is similar to ternary form, as it is divided into three sections: the first section (exposition) has a specific character, the second section (development) contrasts with it, and the third section (recapitulation) repeats the character of the first section.

Early binary sonatas by Domenico Scarlatti show how the transition from binary form to sonata-allegro form happened. Among these sonatas, many examples demonstrate how true sonata form was developed properly.

Sonata theory

The sonata form is a guide for composers to structure their music, for performers to understand how to interpret it, and for listeners to recognize the meaning of musical events. Many details in a piece of music depend on the harmonic relationships between notes, chords, and phrases. The sonata form describes the structure and organization of a musical movement, helping performers know what parts to emphasize and how to shape musical phrases. Its rules were first described in the 18th century and written down clearly in the early 19th century. This organized form is still taught in music education today.

In the 20th century, the focus shifted from studying musical themes and keys to examining how harmony changes throughout a piece and how cadences and transitions help create a sense of "closeness" and "distance" in sonata form. The ideas of Heinrich Schenker, who described music as having "foreground," "middleground," and "background" levels, greatly influenced how music is taught and performed. Schenker believed that successful compositions should follow a clear and logical structure.

For example, a cadence (a musical ending) should be played in a way that matches its importance in the overall piece. Important cadences are highlighted with pauses, changes in loudness, or sustained notes. False or deceptive cadences are played like real ones but then quickly move forward, creating contrast. These changes in how music is performed affect how people understand the structure of sonata form. In the Classical era, the importance of sections and harmonic progressions was replaced by a focus on themes. The clear distinction between major and minor keys became less defined, leading to changes in how music was performed, such as using more varied tempos to shape the music.

Over the past 50 years, studying original scores, handwritten notes, and historical records has changed how sonata form is understood. These studies have influenced how music is edited, such as changing the phrasing in Beethoven’s piano works to use longer phrases that may not always align with traditional structural markers. Comparing recordings of Schnabel, Barenboim, and Pratt shows how the way sonata form is performed has evolved over time.

For composers, the sonata form is like the plot of a story, showing when key events occur and how to connect them into a complete and organized piece. At times, the sonata form has been seen as very strict, while at other times, more flexible interpretations have been accepted.

In sonata form theory, some argue that other movements in a piece, like slow movements, share similarities with the sonata-allegro form, even if they use different phrasing or place less emphasis on development sections. Others, like Charles Rosen, suggest that all movements are "sonata forms," while Edward T. Cone believes the sonata-allegro is the ideal structure others aim to follow. The term "sonata" is sometimes added to other forms, such as the "sonata rondo," to show their connection to sonata principles.

Theorists like Arnold Schoenberg and others who followed him believed that theme and variations play a key role in shaping music, calling this process "continuing variation." They argued that the sonata-allegro form is a way to organize this ongoing variation. Other theorists, such as Erwin Ratz and William E. Caplin, support this idea.

Some parts of musical works, like Carl Maria von Weber’s Konzertstück in F minor, are analyzed using sonata form principles.

Starting in the 1950s, Hans Keller developed a method of analysis that looked at both the structure of music and what listeners expect. He described the sonata-allegro form as a "background form" against which composers could create unique "foregrounds." This contrast between expected and unexpected elements was seen as a way to express emotion in music. Keller applied this idea to both classical and modern works, such as those by Arnold Schoenberg. More recently, James Hepokoski and Warren Darcy developed "Sonata Theory," analyzing how composers followed or changed traditional expectations in sonata-allegro movements and sonata cycles. Their work focuses on the works of Haydn, Mozart, Beethoven, Schubert, and their contemporaries, showing how sonata form evolved into the 19th and 20th centuries.