What is the significance of the tonic in music 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 sets the key's tonal center and influences the overall structure and harmony by providing a sense of stability and direction. Other chords and notes in a piece often revolve around the tonic, creating tension and release that shapes the musical journey.