What is the significance of the tonic in music theory and how does it influence the overall structure and harmony of a musical piece?

The tonic is the main note or chord in a musical key, serving as a point of rest and resolution. It provides a sense of home base and stability in a piece of music. The tonic influences the overall structure and harmony by establishing the key and creating a framework for the other notes and chords to revolve around. It helps create tension and release, leading to a satisfying and cohesive musical experience.