foundation tone

In music, the tonic is the foundational note of a scale, serving as the central point for melodies and harmonies. It's the most important note, around which a piece of music is organized. The tonic note also defines the central chord, known as the tonic triad.12

The concept of tonality is built upon this central tonic note, establishing a system of relationships between notes, chords, and keys. This system, prevalent in Western music, creates tension and resolution as compositions move away from and return to the tonic. The key, indicated by a key signature, specifies the tonic note and scale used in a piece.32