Binary Form describes the structure of a piece of music which is divided into 2 different sections. The 2 sections are usually labelled A and B.
The key concept to grasp is that there is some sort of contrast between the A section and the B section. This contrast is usually (though not always) created by a key change. There are 2 main types of Binary Form you will come across.
Simple Binary Form
Simple Binary Form refers to the basic Binary Form structure outlined above. There is an A section followed by a B section in a different key (both sections are usually repeated). It usually follows the pattern of key changes outlined below:
Examples of Simple Binary Form - A large number of Baroque dances typically had a Binary Form structure. Examples include the sarabande, allemande, gigue, minuet, bouree and the courante. Have a look/listen to his example:
Rounded Binary Form
Rounded Binary Form is very similar to simple Binary Form except for the fact that Section B is often longer than section A and part of section A is repeated again at the end of section B.
Rounded Binary Form was very common in the Classical period of music. It was often used as the structure for the theme in a set of theme and variations. Here is an example from Mozart’s Piano Sonata in D major K284 3rd movement:
Composing using Binary Form
Binary Form is a fantastic structure to use if you are composing because it immediately brings a sense of contrast to the piece you are writing. It is also great because it is a foundation upon which you can build. If you write a piece of music in binary form and want to keep going you can easily extend it into Ternary Form (by repeating the A section to form A-B-A) or create a Rondo (by adding more sections to create A-B-A-C-A-D-A). With the basic music theory you have gained from this lesson you easily have enough to get started – good luck!