What is "Sonata-Allegro form" and what other similar forms should I be aware of?

Question

There are lots of classical pieces called "Sonata", and they usually have 3 movements. But there are guitar Sonatas by Paganini that only have 2 movements! And I heard there's a crazy Tchaikovsky -- maybe it was a symphony, but that's still sonata-form, right? -- piece that has 4 movements. I heard orchestras get spooked-out when playing this piece in Japan because they alone, having done their homework, know *not to clap* after the boisterous III. Allegro.Would someone explain what the 'Sonata-Allegro' form is, and perhaps shed some light on these side-questions by-the-by?[PS. Willing to separate this part as new question if appropriate.]There's also the Rondo (== 'Rondeau'?) form that shows up in the same Piano collections. Are there others that belong to the same class?

Answer 1

Sonata-form, or sonata-allegro form refers to the form of a single piece - whether that piece is a part of a multi-movement work makes no difference. One or more movements of a symphony or sonata or chamber work, or single movement overture can use sonata form. So let's break down different types of forms:

1) Sonata form - a movement using this form is generally broken into 3 parts: exposition, development, and recapitulation. There can be an introduction or coda, but those aren't defining elements of the form.

A) The exposition is where all the main themes/material are presented. At some point in the exposition, there will be a modulation to a different key, usually closely related. In a major key, the modulation will move one key in the sharp direction of the circle of fifths, and in a minor key, it will usually modulate to the relative major. In classical era works, this whole section is often repeated by use of a repeat sign.

B) Following the exposition, the role of the development section is to create instability and tension, taking the material of the exposition and fragmenting it, moving it through various keys, and often increasing the use of counterpoint. It's the section that allows the composer the greatest amount of creative freedom.

C) After this, the recapitulation follows, which is the return of all the material of the exposition. The difference is, all the material from the exposition is now in the home key.

There are subsections to these 3 main sections, but you can look on wikipedia if you're interested in going further: https://en.wikipedia.org/wiki/Sonata_form

2) Rondo - in rondo form, you have a main A section that keeps returning. In between these main A sections, you have episodes, or excursions, so the form looks like ABACA.... etc. Good examples everyone knows are Fur Elise by Beethoven and Rondo alla Turka by Mozart.

3) Ternary form - The simplest of the forms, since by definition, it's just three parts - ABA'. Two near identical outer sections with a contrasting middle section. Mozart's slow movements often used this form, in addition to many classical era minuets or scherzo movements.

4) Theme and variation - Just like it sounds, a theme is presented, which is followed by a series of variations of that theme. The melody, rhythm, tempo, and mood can be altered in each variation, all that's important is that the listener can hear how each variation relates to the original theme. Famous variations are Mozart's variations on the "Twinkle Twinkle" theme, Bach's Goldberg Variations, and the 4th movement of Brahms Symphony No. 4.

5) Rhapsody/Fantasy - This is the only form where there form is undefined, or rather, a form is there, but is unique to each piece.

Of course, composers have always found a way to break these rules, or find ways of creating hybrids of these forms, like sonata-rondo form, or blends of ternary and sonata form, like the Scherzo in Beethoven's 9th.

Hope this helps!