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

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 stability and home base in a composition. The tonic influences the overall structure of a musical composition by establishing the key and creating a framework for the progression of chords and melodies. It helps create tension and release, guiding the listener through the emotional journey of the music.