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You need to be able to recognize and describe the important features of 4 different types of musical form.

1. Ground bass. A ground bass is a bassline or chord sequence that is repeated all the way through a piece, while the melodies and textures change and develop above it. You can find some more information here.

2. Theme and variations. A theme and variations consists of a main tune (or theme), plus a sequence of variations of the theme. The variations should keep the same basic structure as the theme (i.e. same number of bars and phrases, mostly the same chords) and some of its melodic features, but each variation will introduce new twists and changes to the melody, rhythm, harmony and texture of the theme. Often, the variations will become progressively more elaborate as the piece develops. Be prepared for questions which ask you to compare two or more variations, or identify techniques which have been used to alter a theme. Click here for an illustrated example.

3. Ternary form. This is often explained as a musical sandwich. There are 3 sections. The first and last sections are the same (the slices of bread!), with a contrasting middle section (the filling!). A more prosaic description is ABA form. You might find slight variants on this, for example where the final section is a slightly altered version of the first (ABA1), or where the main sections are subdivided into a mini-ternary form (ABACDCABA. A common type of movement which usually employs this structure is the Minuet and Trio. A minuet was a type of dance which was popular in the 18th century. Most symphonies and chamber works from this period have a minuet and trio as their 3rd movement).

4. Rondo form . If Ternary form is a musical sandwich, then Rondo form is a double (or triple) layer sandwich. The A section, or main theme comes 3 or more times. In between statements of the main theme come different contrasting sections, called episodes. Typical examples of Rondo form would be ABACA or ABACADA. In the 18th century, Rondo forms were often used for the last movement of a sonata or symphony.