Revised June 30, 2018

Pinellas County All County High School Orchestra, 2016
People today with little or no musical training somehow “get” a 12-measure blues chorus or the standard song forms of various modern styles. Even music majors taking theory classes have a hard time with sonata form. How is anyone else to make sense of it?
Sonata form did not always cause confusion or seem to set up a barrier to understanding music. It actually started off as an attempt to simplify music. I have written several posts about the rise of the middle class, the popularity of what we call “classical” music, and the aftermath of the French Revolution, which destroyed public concert life in the three major capitals of Europe.
During the time described in these articles, everyone knew sonata form as well as we know the forms of today’s music. Even people with no musical training could follow it. Even people who enjoyed music only as amusement and not as an art form could appreciate clever things composers did with it. It was a current procedure, not a museum relic.
The principles of sonata form underlie all classical music from early Haydn through Bruckner, and not a small portion since then. How can today’s audiences without musical training make sense of it? Now, when it’s a specialized subject in a music curriculum, people tend to approach it with some trepidation. They think they have to understand this antiquated system in order to enjoy the music.
So take heart from the words of operatic tenor Luciano Pavarotti: “You don’t need any brains to listen to music.”
The listening experience of sonata form
First of all, enjoy the music for its beauty and wide range of emotional expression. Don’t worry about the underlying form.
How many people who enjoy 12-measure blues choruses and 32-measure Tin Pan Alley standards can explain the difference? How many people who thrill to a great improvisation on any familiar tune know or care about the nuts and bolts its structure? Probably not many.

Mozart piano sonata, KV 331
People who don’t understand the structure of music, any music, can enjoy it on a visceral level. In fact, pitiful is the person who gains an intellectual knowledge of music at the cost of losing the ability to enjoy it viscerally.
Nonetheless, I offer this very non-technical, non-academic explanation. If knowledge and technical understanding are not prerequisite to enjoyment, they can certainly enhance it.
Historical information

The Mozart family, ca. 1780 / Johann Nepomuk della Croce
Sonata form grew from dance forms. These, in turn, were mostly two-part forms, with both parts repeated. The music started out in a particular key.
Either by the end of the first part or the beginning of the second part, it moved to another key. After all, too long a stretch of music in the same key can get boring. Then it returned to the first key.
In music classes, the standard diagram for these short forms is ||: A :||: B :||. The symbols ||: and :|| indicate repeats and A and B represent different music. Sometimes, though, the first part of A returns at the end of B, or graphically, ||: A :||: ba :||. That has a name of course, but if you don’t already know it, there’s no need to learn it.
Conventionally, some dances were presented in pairs, as in two minuets. Both were two-part forms. The second was in a contrasting key. After the second dance of the pair, in order to get everything back to the same key where it started, the first one repeated, usually without the internal repeats and maybe with some kind of embellishment of the tune.
Together, then, these paired dances made up a three-part form (which we can diagram A B A), with both parts being a two-part form. Operatic arias, another source of sonata form, exhibited a different kind of three-part form.
The first two parts did not repeat, and they contrasted not only in key but in mood. At the end of the second part, the singer went back to the beginning and sang the first part, heavily embellished.
This kind of aria gave the singer a chance to show off his or her technical ability and imagination in embellishment. Within the opera, it gave the composer a chance to portray a dramatic situation to the point of painting a character’s mixed emotions about it.
Sonata form combined aspects of the older dances and arias and built them into something that could last much longer than any previous single movement, and yet maintain unity and coherence.
From dances, sonata form inherited the basic two-part structure. Composers quickly abandoned repeating the second part. After Beethoven, very often they no longer repeated the first, either.
The music in a classical sonata form moves to the new key by the middle of the first part. As in the operatic aria, the new key coincides with a change of mood. A sonata movement, therefore, becomes a drama in itself. (Although we usually associate sonata form with instrumental music, Mozart used it in many of his operatic arias and ensembles.)
Technical (sort of) information

Kuchengarten, a pleasure garden in Leipzig / Heinrich Georg Drescher (1847–1925). Owned for a while by trombone soloist Karl Queisser, it offered a relaxed place for the musically unsophisticated to enjoy all kinds of music, including classical sonata-form pieces.
Sonata form may or may not have an introduction. Leaving that aside, the form begins with a recognizable melody called a theme, which might be as long as the entire first part of one of the earlier dances. When it’s finished, the music makes a transition to a new key. This first part, called the exposition, presents the thematic material like characters in a drama.
Sonata form usually has two themes, with transitional music in between. Sometimes the same theme occurs in both keys. Other times, there may be more than one distinctly different theme in each key. The drama inherent in sonata form comes not from the contrast of themes, but the contrast of keys.
We can think of it without any technical language: the music leaves home (the first key) for some other destination (the second key). Eventually, it gets back home. The old dance forms simply modulated to a new key and back, kind of like commuting. But sonata form makes it a challenge to get there.
Therefore, the second part of our movement does not begin in the first key. It leads back there over the course of great difficulty. Dramatic tension builds as the themes get ripped apart and made to pass restlessly through many new keys. Technically, musicians know this section as the development, or working-out section.
If we look at sonata form as a journey, the music goes fairly directly from the first to the second key in the exposition. Then it takes the scenic route back home in the development. If we look at sonata form as a drama, the characters are the thematic ideas and key centers. They wrestle and contend with each other until they come to a place of rest.
That place of rest, called the recapitulation, starts when the music finally arrives the first key. Aside from music, we usually say recap nowadays. It has taken so much struggle to get there, the music can’t stop yet.
The audience needs reassurance that it has gotten back home. So, in a borrowing from the three-part form, the recap repeats all the thematic material introduced in the exposition. Except this time, it doesn’t change keys.
Once the second theme sounds in the first key, the form has finished. Keeping in mind that the development and recap together constitute the second part of a two-part form, it’s pretty easy to see why composers stopped having it repeated. Repeating the first part gives the audience a second chance to hear all the important themes. Repeating the second part would only repeat the drama and its resolution.
In case you were wondering why I provided textbook graphs for the two-part form after promising not to be academic, we can see sonata form in this one: ||: A :|| ba ||. “A” is the exposition, which is repeated. “B,” divided into “ba,” is the development and recap and is not repeated. Besides omitting the second repeat, then, sonata form is very much like that old dance form where the beginning of the first part returns at the end of the second part.
The composer may or may not tidy things up a bit more with some extra music tied on to the end. It’s called a coda, which is Italian for tail. Beginning with Beethoven, however, the coda didn’t tidy up anything at all. It’s as if the two characters in the drama get to the end of the recap and discover some unfinished business. They get into a fight all over again. The coda gets as long as either the development or the recap.
In a classical concerto, where a soloist plays with the orchestra, the drama plays out a little differently. The orchestra plays all the thematic material without changing keys. Then the soloist comes for the repeat of the exposition. The second time through introduces the contrasting key. The development and recap happen in the usual way, but the soloist has a chance to show off with a cadenza.
Beethoven blurs and breaks sonata form

Portrait of Beethoven / Joseph Karl Stieler, 1820
Up through the middle of Beethoven’s career, the various sections of a sonata form are fairly obvious once you know what to listen for. Composers usually placed a brief moment of silence between them. Beethoven experimented with blurring the boundaries.
Later composers got so good at hiding the joints that sonata form became almost impossible to hear. It became a nearly indiscernible structure underpinning whatever appears at the surface. It takes a great bit of painstaking study for even the most proficient musicians to find them.
Therefore, when it comes to nineteenth-century music in particular, hardly anyone in the audience can hear the form.
There. I’ve let the secret out. Even professionals can’t always follow the sonata form just by listening to music after Beeethoven. They don’t necessarily even want to.
So without too much trouble, you can learn to hear sonata forms written in the Classic period––if you want to. Otherwise, just let the sheer beauty of the sound and the music’s dramatic and emotional power wash over your ears and give you a thrill.
For further reading: Sonata Forms / Charles Rosen. Revised edition (New York: Norton, 1988).
Photo credits:
Pinellas orchestra. Screen shot from Vimeo
Mozart sonata. Some rights reserved by Girl flyer
Mozart family. Public domain from Music with Ease
Kuchengarten. Public domain from Wikimedia Commons
Beethoven. Public domain from Wikimedia Commons