of music??AABBACCDD(16bars of each theme) Scott Joplin "Maple Leaf Rag" the A theme, brings you back to where you can progress, it's either a reminder of where the tune started, or a re-inforcement of the tune, ( a hook)
a usefull tool in re-establishing the original tune, and a handy way of reminding the listener of the theme. FORM! study form in todays music and you will find variants of the rounded binary form,.... Form is something purely of composers descretion. A Returning "A" section, or variation of "A", often would bring closure and a sense of fimiliarity to a piece of music. Most music is like this. It gives a song shape and motion. Form is just another device for composition. Another way of composing is "through" composing. This is found in classical music where there are NO reoccuring sections. In jazz, "Lush life" would kinda be consider through composed, because it has no repeated sections (with exception to the soloing over the form) | 