Form gives structure to a piece of music by dividing it into sections. Landmarks at the beginning of each section can be a big help to us when we learn to memorize these divisions. Four different types of music structures are binary, ternary, rondo, and theme and variations.
I explain to my students that we like the warmth and security of home which (compared to the A section of a piece of music). Sometimes we have the urge to leave home and explore a new place, (the B section of the piece). We may want to stop back at home (the A section) briefly before leaving for another place (the C section). Then we may choose to go back to our home. (the A section)
A composition can start out with an A section (home) followed by a contrasting B section (away from home). This is called 'binary', or 'A B'. Think of starting at home (A) and then going to a friend's home (B). You can also think of an apple (A section) and a banana (B section). Think of other analogies of using A and then B in a piece of piano music.
Another piano piece may have a part we call the A section followed by a contrasting section we call the B section and a return to the A section. This piece is 'ternary' (in three parts): A B A. Think of starting at your home (A), going to a friend's home (B) and then returning to your home (A). Think of an apple (A), a banana (B), and another apple (A).
The structure of a Rondo, one of the oldest musical shapes, keeps returning to the same theme after segments of new material. Poems and songs that have the refrains after each new verse are in rondo form. There is an A section that repeats in between a contrasting B, and sometimes even C and D sections. Think of A B A C A D A: an apple (A), a banana (B), another apple (A), an orange (C), another apple (A), a grapefruit (D) and another apple (A). Beethoven used this structure for the famous piano piece, Fur Elise. Can you think of other examples?
Theme and Variations begins with a melody followed by repetitions of it in different ways (variations) each time it returns. It can have the sections A, A1, A2, A3, A4, or more variations. Think of an apple, an apple pie, an apple dumpling, apple sauce and apple cake. Sergei Rachmaninoff and Johannes Brahms, composers who lived during the Romantic Era in music history, wrote in this type of format for solo piano with orchestra, Theme and Variations on a Theme by Paganini after hearing a beautiful melody written by the famous violinist Niccolo Paganini.