OK, so now that we have explored Ternary, there is one last short form we’ll discuss: Rounded Binary
In a Nutshell
Rounded Binary looks like this:
||:A:||: B A:||
Sometimes, the composer will only use a part of the A section when it returns at the end. This is sometimes written as
||:A:||:BA’:||, where the A’ is called “A prime” and means that the A section has been changed slightly.
In this case we could say the form is Bread, Bread, Cheese, Half a Slice of Bread, Cheese, Half a Slice of Bread.
Here is a listening example in the form ||:A:||:BA’:||
Mozart Eine Kleine Nachtmusik, 3rd movement