Please refer to my Article "Levels of Musical Form" for background to this Article.

When I say "Piece-Level Form" I'm talking about the types of form you've probably heard about - Binary Form, Ternary Form, etc.

While there is already an Article here devoted to Binary and Ternary Form, I wanted to provide a broad overview of some Forms that readers may find useful from a compositional standpoint.

There are two main "families" of Large Scale Forms:

Open or Continuous*
Closed or Repeating

Continuous Forms constantly evolve and we never hear material again once we've heard it.*(Continuous and Sectional are words that are used to describe an internal characteristic of forms as well, so I'm using continuous in a generic sense here)

Repeating Forms have some element that returns again later in the piece.

Formal Sections may be distinguished in a number of ways:
1. Key
2. Meter
3. Texture
4. Instrumentation
5. Dynamic

and so on. For example, the Trio section of traditional Marches (and minuets) originally not only had various distinguishing elements, but the Instrumentation - of a Trio - was an important facet in delineating that section from the others (and of course, that's where we got the name for that section).

So when we identify a section, we give it a letter A B C D, etc. A continuous Form above would then be:
A B C D E F G etc.

A repeating form would be:

A B C A D A - the A section comes back.

Now for some specific forms:

One-Part Form: seems unusual but some pieces are - especially things like Preludes and Etudes and so on - pieces which are improvisational, pedagogical, etc. are often only in one formal section.

Binary Form:Contains two sections, A and B.

Ternary Form: You'd think it would contain three DIFFERENT sections, but interestingly, it does not! It contains a repeat of the A section. Thus some explanation is needed:

Introductions and Codas, or, Preludes and Postludes (and to a degree Interludes) do not affect Form at this level. Nor do repeats of a section (or of contiguous sections) directly. So, here is a Binary Piece:
A | B
Here also is a Binary Piece:
A | A | B | B

Another way to write the second is:
|: A : ||: B : ||

So it matters not whether one or both sections are repeated immediately, if there are only two sections, and the final B section appears after the final A section, it is Binary. Therefore, even:

A | B | A | B | - which is really ||: A | B :|| is still Binary.

A Ternary Form piece will have a full occurrence of the final A AFTER the final B, and again, it matters not how they are repeated:
A | B | A is ternary.
|: A :||: B :||: A :|| - you guessed it - still Ternary.

There are two interesting (and quite common which is why they need to be mentioned) "hybrids": We call a repeat a "reprise" and most common in classical music is a "two reprise form" in which two "halves" of the music are both repeated (have repeat bars around them). So very often, a Ternary Form piece will be cast in a Two Reprise layout like so:

||: A :||: B | A :||

Now if I lay this out, you get:

A A B A B A. But this is still a 3-section work - A B A, with the two "halves" repeated. Once again, either of these "halves" could be repeated or not. Note that the final A appears after the Final B (and of course it only has A and B sections, with an A at the end). Many people are confused because they think the repeat bars are indicative of Binary Form - they're not - they're indicative of a Two Reprise setting. Binary is A B, Ternary is A B A.

A B C is NOT A ternary form (it's a "three-part form" which is a little different). This is easy to remember though because it's in the other family - continuous. Thus, A (one part), A B (binary) and A B C (three part) are all continuous forms.

Our first repeating form type is Ternary or ABA.

Here however is the other interesting hybrid form called "Rounded Binary" and it is:
A B 1/2A.

Now be careful here - this is NOT A A B B A - that's not half of A, that's a FULL A simply not repeated at the end (thus that's a true Ternary form). Literally, only half of the A section's material returns at the end (usually the second phrase of a two phrase section, so it ends with the correct final cadence). In terms of chord progressions, a Rounded Binary might look something like:
I - I - V - I - V - V - I - I (A section)
V - V - I - I - I - IV - V - V (B section)
V - V - I - I (2nd half of A section).

And again, any section, or combination of sections can be repeated - repeats do not affect form at this level:
||: A :||: B | 1/2 A :||
is quite common - thus a Two Reprise Rounded Binary (note: some authors call this something like "Incipient Ternary" because it *really* is closer to Ternary form, but the name Rounded Binary is so common).

So, so far we have:
A
A B
A B C
A B A
A B 1/2A

The last two being the predominant classical Forms (I should also note that Binary Form was more common in the Baroque and in smaller works (Dances like Bourees, etc.) and in the Classical period Ternary (including Rounded Binary) became the more favored form).

Larger (longer) forms are actually pretty rare - a C section is somewhat common, though D - except in what we call "through composed" works is fairly rare. Through-composed works (A B C D E, etc.) are often Vocal works where new music accompanies each new stanza of text (the opposite is called "strophic" where the text changes but the music stays the same).

Probably the most common form after Ternary are called "Rondo" forms, in which a section, usually the A section, continually returns:

A B A C A is a "five part Rondo" (note though that A B A is not called a "three part rondo" even though that's what it basically is).

A B A C A D A is a seven part rondo, and some theorists call them "serial" to show that the "non-rondo" element (A B C D here) is continuing in series.

A nice form that evolved in the 20th century is the "Arch Rondo":
A B A C A B A.

And there is an interesting non-rondo counterpart to this called "Arch Form":
A B C B A.

SO:
A
A B
A B C
A B A
A B 1/2 A
A B C D...
A B A C A
A B A C A B A
A B C B A

And again, Introductions, or Codas, interludes, etc. do not affect musical form UNLESS they are significant enough to become their own section (in which case they're no longer an "Introduction" but an A section, etc.).

You might be curious at this point what Theme and Variations are. These are called "Variation Forms". In the simplest sense, these are simply a one part form usually:

A - repeated a bunch of times. But since A is varied throughout, it becomes:
A A' A'' A''' ("A prime" "A double prime", etc.). This distinguishes the multi-part Variation Form with the simple One Part Form that is simply A (or |: A :|).

Passacaglias, Passamezzo, Ostinati, and Theme and Variations are all types of Variation Forms. Strophic Song forms are really a type of Variation Form as far as the music is concerned.

And now for the Grand-daddy of all forms: Sonata Form. The most over-rated, over-studied, and mis-understood of all forms. It gets its name because it is frequently found as the first movement (an Allegro) of Classical Period works (and also is called Sonata Allegro or First Movement form).

A Sonata Form movement is just a big giant Ternary form:
A B A
The first A is called the Exposition
The B is the Development
The second A is called the Recapitulation (which is a fancy name for repeat).

What makes Sonata form special is not the Form, but the Tonal scheme within the form (which is at the Phrase-Level), which is another article. But to put it simply, basically your A section has two Themes, one in the home key one in a different key. The B section develops those themes and stays away from the home key (and may introduce a third theme, etc.). Finally, most importantly, the Recap of the A section presents Themes 1 and 2 again, this time BOTH in the home key. Usually the sections are repeated in a two-reprise fashion:

|: Exp. :||: Dev | Recap :||

Though as time went on (like through Beethoven) one or both sections may not be repeated.

There are also a few hybrid forms like "Sonata Rondo" in which elements of Rondo are incorporated but again that's beyond the scope of this article.

What about Fugue? Isn't that a Form? Well, not really. That's a Genre. A Fugue is usually in a Ternary Form. Fugue refers to a method of composing, not necessarily the Musical Form of the piece itself.

What about "Bar Form" or "Song Form"? Bar Form is A A B. So really, it's simply Binary with the first part repeated. It's just such a commonplace form we gave it its own name.

What about "12-Bar Blues"? Well again, despite what we hear, it's not really a "Form". It's one of a Section of Forms. A 12-Bar Blues piece like "Hound Dog" by Elvis is simply A - A - B again:
You ain't nothin but a Hound Dog, Cryin all the Time.
You ain't nothin but a Hound Dog, Cryin all the Time.
You ain't never caught a rabbit and you ain't no friend of mine.

Musically speaking, the chords are different under each line, but it's still one big section. What makes FORM is the things like VERSE, CHORUS, etc.
So in Hound Dog, musically we have a Variation form:
A A' A'' in which A is Verse 1 (You ain't nothin...) A' is Verse 2 (Well they said you was high classed...) and A'' is the Guitar Solo (or wherever that occurs).

So that's "Prase Level Form" and another Article.

Stay Tuned...