Think of multi-layered cakes. What is their structure? Let’s think of a cake that is made up of the sponge, the frosting and some jam. Now, let’s start layering from the bottom up. Sponge, frosting, sponge, jam, sponge, frosting, sponge. Same goes with music. Let the main idea (the sponge) be A and the rest (the frosting and the jam) be B and C, respectively. You can create ‘structures’ like ABA, ABCA, ABACA, ABABCA, and so on. The layered cake with jam was ABACABA. Those ‘structures’ are the forms of music. Now, I want to have some cake.