# Sonata-Allegro Form



## Majed Al Shamsi

Hello, everyone. I suspect most of you are familiar with this form. Had a couple of questions.

According to this lecture, the general form is:

1. Exposition (repeated)

- First theme
- Bridge
- Second theme
- Closing theme

2. Development

3. Recapitulation

- First theme
- Bridge
- Second theme
- Closing theme

An introduction and/or a coda are optional.

Generally speaking, in the exposition, if the first theme is written in a minor key, the second theme would be written in the key of its relative major (i.e. the third.)
But what keys are the bridge and closing theme usually written in?

My other question has to do with the development section, where you pick one or more parts of the exposition and develop them. Are they written in their original keys, or is everything written in the relative major (since the development usually ends with the relative major)?

Thanks in advance.


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## Vasks

The bridge modulates from the opening key to the secondary key.

The closing theme is in the same key as the second theme.

The development usually avoids the opening key, but otherwise can explore many other keys.


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## Majed Al Shamsi

That is more precise an answer than I had hoped for. Thank you, Vasks!


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## KenOC

To add to Vasks: In the recap, the themes are all in the same key, supposedly "reconciling" the tensions originally set up. Obviously the bridge passage has to be different from the expo, a source of much cleverness in the classical period, especially early Beethoven.


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## Majed Al Shamsi

I knew the themes in the recapitulation had to be all in the same key, but I have never considered what becomes of the bridge.
Thank you for pointing that out. It is, after all, leading right back to the tonic (I believe, in the lecture, it was called 'the bridge to nowhere.')
Is the new bridge usually completely different from the initial one, or does it retain some of its notes?


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## Vasks

Majed Al Shamsi said:


> Is the new bridge usually completely different from the initial one, or does it retain some of its notes?


That's all up to you. You may not even need to write a bridge in the Recap. since you don't have to modulate.


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## Kopachris

For more details about what precisely goes on in a sonata-allegro movement (there's a lot more to it than one could fit in a forum post), I recommend reading Classical Form by William Caplin. The book goes into detail about what sort of structures themes could take, recommends forms for transition themes (i.e. the "bridge"), and also gives some ideas for the structure of the development.

That said, I could probably go into a _little_ more detail about the exposition while I'm here. The "first theme" you listed is typically a "first subject group," and is usually a collection of several themes. It's not strictly required to keep them all in the tonic key all the time (tonality can be quite flexible) as long as the structure of the first subject group as a whole is fairly tight-knit and primarily expresses the tonic. The bridge is a transitional theme. Since modulation itself is usually rather short, the point of the transition is to destabilize the tonic. This is usually done structurally, by using more loosely-knit forms for the theme, usually ending with the actual modulation to the new key. Some sonata expositions actually skip the transition and modulate fairly directly (perhaps a short chord progression). The second subject group follows similar rules to the first, except it's okay to use more loosely-knit forms for your themes.

While studying, you should keep in mind there are infinite variations on this form. A few examples:


Wikipedia said:


> a monothematic exposition, where the same material is presented in different keys, often used by Haydn;
> a 'third subject group' in a different key than the other two, used by Schubert, Brahms, and Bruckner;
> the first subject recapitulated in the 'wrong' key, often the subdominant, as in Mozart's Piano Sonata No. 16 in C, K. 545 and Schubert's third symphony;
> the second subject group recapitulated in a key other than tonic, as in Richard Strauss's 2nd symphony.
> and an extended coda section that pursues developmental, rather than concluding, processes, often found in Beethoven's middle-period works, such as his third symphony.


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## Vasks

Kopachris said:


> (there's a lot more to it than one could fit in a forum post)


Ain't that the truth


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## EdwardBast

I am very late to this discussion, but the version of sonata form you posted is a codification of the form from the mid-nineteenth century. It was abstracted from a few of the best known and dramatic works of Beethoven and Mozart, like the first movements of Beethoven's Fifth and Mozart's 40th symphonies, and its connection to musical reality is complicated. 

Second themes can be in virtually any key. If the first theme is in the minor mode, the second theme needn't be in the relative major. Beethoven used other keys, including the submediant (in C minor that would be A-flat major), the sharped mediant, and others. So did Schubert. Schubert very often had three quite distinct key areas in his expositions. Mozart often had five or more clear themes. Haydn often had only one, with variants. Recapitulations don't always start in the tonic. During the early classical period it wasn't uncommon to have them start in the subdominant. 

In summary, sonata form is in reality an extremely loose and general format. If writing student and study pieces, it is not a bad idea to keep the schema you posted in mind, but don't take it as written in stone. Your themes might not want to be treated that way. And you can have extra themes instead of transitions, you don't necessarily need a closing theme, etc.


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