Sonata allegro form

Sonata form or sonata-allegro form is a musical form, a way of organising a work of music. The original idea of a central organizing form has been very widely used by classical composers since the 18th century. It was considered to be the standard form for the first movement of any important work of instrumental music, for example a symphony, concerto, sonata or other works based on them, such as string quartets. For this reason, it is sometimes called first movement form, although this is somewhat of a misnomer, as it has been used in other movements of pieces. It is also sometimes known as compound binary form.

The central idea of the sonata-allegro form is to organize either harmony or themes from their being introduced, to their "development" or working out, through to a "recapitulation" where the original theme returns, and then, sometimes, to a "coda" which extends the music onward after the formal closure of the work. This idea has been progressively expanded on by new generations of composers, each seeking to refine, or enlarge, the same general shape to fit their own ideas. There are commonly played "sonata-allegro" movements which last only a few minutes, and some which extend for half an hour.

In music theory, the word "sonata" refers to works in the sonata form, even if those works are not labelled "sonata". For example a symphony is thought of as a "sonata for orchestra". The term "sonata form" is also applied to the use the layout of all of the movements, for example, Schumann relabelled a piano work as a "sonata" only when he included a fourth dance movement. This article will focus primarily on the sonata-allegro form, its structure and development over time.

Outline of sonata form

The classical sonata form movement in its simplest version consists of the following sections:

• Exposition - the main themes (usually called "subjects") of the piece are played for the first time. This section can be further divided into:
  • First subject group - this consists of one or more themes, all of them in the home key. So if the piece is in C major, all of the music in the first group will be in C major.
  • Transition - in this section the composer modulates from the key of the first subject to the key of the second.
  • Second subject group - one or more themes in a different key to the first group. If the first group is in a major key, the second group will usually be in the dominant, that is to say in a key a perfect fifth higher, so that if the original key is C major, the key of the music of the second group will be G major. If the first group is in a minor key, the second group will generally be in the relative major, so that if the original key is C minor, the second group will be in E flat major. The material of the second subject is often different in rhythm or mood from that of the first subject (frequently, it is more lyrical), but this is not always so; see below under "Monothematic expositions".
  • Codetta - a kind of finishing off section, which will 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.

• Development - this 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 with new material or themes. The development varies greatly in length, but almost always shows a greater degree of tonal and rhythmic instability than the other sections. At the end, the music will return to the home key and lead up to the:

• Recapitulation - this is an altered repeat of the exposition, and consists of:
  • First subject group - usually in exactly the same form as it appeared in the exposition.
  • Transition - now altered so that it does not change key, but remains in the piece's home key.
  • Second subject group and codetta - usually in the same form as in the exposition, but now in the same key as the first group. If the first group was in a minor key, the second group and codetta may be shifted into the minor for the recapitulation, or they may be in the parallel major key (e.g., C minor/C major).

The above terminology is not universally used: some writers speak of the first and second subjects rather than groups, others speak of the principal or main theme and the subordinate theme.

Variation in classical sonata form

Sonata form may be varied in a number of ways.

Codas

Quite often, there is an additional section, the coda, which follows the end of the recapitulation. The coda rounds the movement off with a perfect cadence in the home key. Codas may be quite brief tailpieces, or they may very long and elaborate; a famous example is the finale of Beethoven's Eighth Symphony.

Introductions

Less often, the entire movement is preceded by a slow introduction. The introduction increases the weight of the movement, and also permits the composer to begin the exposition with a theme that would be too light to start on its own, as in Joseph Haydn's Drumroll Symphony. Usually, but not always, the introduction is excluded from the exposition repeat.

Occasionally the material of introduction reappears (in its original tempo) later in the movement. Often, this occurs in the coda, as in Mozart's string quintet K. 593, the Drumroll Symphony, or Beethoven's Pathetique piano sonata Op. 13.

Monothematic expositions

It is not necessarily the case that the move to the dominant key in the exposition is marked by a new theme. Haydn in particular was fond of using the opening theme, 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 instance in the piano sonata K. 570 or the string quintet K. 593. Such expositions are often called monothematic, meaning that one theme serves to establish the opposition between tonic and dominant keyes. This term is misleading: most "monothematic" works have multiple themes: most works so labelled have additional themes in the second subject group. Only on occasion (for example, in Haydn's string quartet Op. 50 no. 1) did composers perform the tour de force of writing a complete sonata exposition with just one theme: another more recent example is Edmund Rubbra's 2nd Symphony.

That monothematic expositions usually have additional theme is used by Charles Rosen to illustrate his theory that the Classical sonata form's crucial element of the is that the arrival of the dominant be dramatized in some way. Using a new theme was a very common way to achieve this effect, but other resources such as changes in texture, salient cadences and so on were also accepted practice.

Modulation to keys other than the dominant

The key of the second subject may be something other than the dominant or the relative major. About halfway through his career, Ludwig van Beethoven began to experiment with new keys for the second subject group. These keys likewise move upward along the circle of fifths, but three or four fifths instead of just one. Thus,the second subject of the Waldstein sonata for piano is in E major, fourth fifths higher (C --> G --> D --> A --> E) than the tonic key of C. The Hammerklavier sonata Op. 106 moves three fifths higher (Bb --> F --> C --> G).

It is a open question why Beethoven never modulated just two fifths higher, a major second; possibly this is because it might be perceived as a crude stepwise modulation. (For a modern criticism of such modulations, see the discussion of the "truck driver's gear change" in Modulation (music).)

Modulations within the first subject group

The first subject group need not be entirely in the tonic key. In the more complex sonata expositions there can be brief modulations to fairly remote keys, followed by reassertion of the tonic. Thus, Mozart's String quintet in C, K. 515 visits C minor, Db major, and D major before finally moving to the dominant of G major.

Sonata form in concertos

An important variant on traditional sonata-allegro form is found in the first movement of the Classical concerto. Here, the exposition is not repeated, but is played through in two different versions. The first is played by the orchestra alone, and remains in the tonic throughout the first and second thematic groups. Then, after a cadence on the tonic, the movement returns to its opening material, this time with the solo instrument. This second time, the form is as in standard sonata form, with a modulation to the dominant or relative major before the second group.

Towards the end of the recapitulation, there is usually a cadenza for the soloist alone. This has an improvisatory character (it may or may not actually be improvised) and serves, generally, to prolong the harmonic tension on a dominant chord before the orchestra ends the piece in the tonic.

The history of sonata form

Sonata form arose during the late Baroque era, came to dominate many forms of musical composition during the Classical era, and continued to be influential through the subsequent history of classical music.

Main article: History of sonata form

Sonata form and other musical forms

Sonata form shares characteristics with both binary form and ternary form. It terms of key relationships, it is very like binary form, with a first half moving from the home key to the dominant and the second half moving back again (this is why sonata form is sometimes known as compound binary form); in other ways it is very like ternary form, being divided into three sections, the first (exposition) of a particular character, the second (development) in contrast to it, the third section (recapitulation) the same as the first.

The purpose of the Sonata Form

The sonata form is a guide to composers as to the schematic for their works, for interpreters to understand the grammar and meaning of a work, and listeners to understand the significance of musical events. A host of musical details are determined by the harmonic meaning of a particular note, chord or phrase. The sonata form, because it describes the shape and hiearchy of a movement, tells performers what to emphasize and how to shape phrases of music.

In the simplest example, playing of a cadence should be in relationship to the importance of that cadence in the overall form of the work. More important cadences are emphasized by pauses, dynamics, sustaining and so on. False or deceptive cadences are given some of the characteristics of a real cadence, and then this impression is undercut by going forward more quickly.

For this reason changes in performance practice bring changes to the understanding of the relative importance of various aspects of the sonata form. In the classical era, the importance of sections and cadences and underlying harmonic progressions gives way to an emphasis on themes. The clarity of strongly differentiated major and minor sections gives way to a more equivocal sense of key and mode. These changes produce changes in performance practice: when sections are clear, then there is less need to emphasize the points of articulation. When they are less clear, greater importance is placed on varying the tempo during the course of the music to give "shape" to the music.

Over the last half century a critical tradition of examining scores, autographs, annotations and the historical record has changed, sometimes subtly, occasionally dramatically, the way in which the sonata form is viewed. It has lead to changes in the way works are edited, for example, the phrasing of Beethoven's Piano works has undergone a shift to longer and longer phrases which are not always in lock step with the cadences and other formal markers of the sections of the underlying sonata form. Compare the recordings of Schnabel from the beginning of the recording era, with those of Barenboim, and then Pratt shows a distinct shift in how the structure of the sonata form is presented to the listener over time.

For composers, the sonata form is like the plot of a play or movie script, describing when the crucial plot points are, and the kinds of material that should be used to connect them into a coherent and orderly whole. At different times the sonata form has been taken to be quite rigid, and at other times a freer interpretation has been generally considered permissible. Questions such as whether themes may be presented in the "wrong" keys or the "reverse order" show eras with a stricter understanding of sonata form.

Musical criticism and sonata form

Because of its centrality to classical music, sonata form has been a topic of interest to musical critics ever since its origin. For full discussion, see Criticism and sonata form.

See also

• Sonata rondo form
• Three-key exposition