What is the term for the tonic in the key notation?

The tonic in key notation is represented by the symbol I for major keys and i for minor keys. This notation signifies the first scale degree of a major or minor scale, which serves as the home note or tonal center of the key.

In music theory, the tonic is foundational because it is the starting point for melodies and harmonies within that key. All other chords and notes in a piece of music relate back to this tonic note, creating a sense of resolution and stability.

Understanding that I and i represent the tonic allows musicians to recognize the importance of the key’s home note and helps in creating chord progressions and melodies that are harmonious and cohesive. The other choices represent different scale degrees: II or ii indicates the supertonic, III or iii the mediant, and IV or iv the subdominant, but these do not serve the same foundational role as the tonic.