Chord structures are the building blocks of music, defining how notes are organized to create harmony. They consist of combinations of notes played simultaneously, forming chords that evoke different emotions and atmospheres. Common chord structures include major, minor, diminished, and augmented chords, each contributing to the overall sound of a piece. Understanding chord structures is essential for musicians and composers, as they provide a framework for songwriting and improvisation. By manipulating these structures, artists can create tension, resolution, and movement within their music, making chord structures a vital aspect of musical expression.