Which statement about the tonic is true?

Which statement about the tonic is true?

• A. It is built on the subdominant pitch.
• B. It is never diatonic.
• C. It is the most unstable chord in the key.
• D. It is the diatonic triad built on the tonic pitch.

Answer: (D)

The tonic is the home base of a key, and the chord that belongs to that home base is the diatonic triad built on the first scale degree. This captures what the statement is saying: the chord formed by the tonic pitch and its nearby scale notes (the 1–3–5 notes of the scale) is diatonic to the key. For example, in C major the tonic triad is C–E–G, built from notes of the C major scale, so it’s a stable, homeward chord. In A minor, the tonic triad is A–C–E, which is minor but still diatonic to A minor. That stability and sense of resolution are why the tonic functions as the key’s anchor. The other descriptions don’t fit: the subdominant pitch would give the IV chord, not the tonic; the tonic triad is indeed diatonic; and the tonic is the most stable, not the most unstable, chord in the key.

The tonic is the home base of a key, and the chord that belongs to that home base is the diatonic triad built on the first scale degree. This captures what the statement is saying: the chord formed by the tonic pitch and its nearby scale notes (the 1–3–5 notes of the scale) is diatonic to the key. For example, in C major the tonic triad is C–E–G, built from notes of the C major scale, so it’s a stable, homeward chord. In A minor, the tonic triad is A–C–E, which is minor but still diatonic to A minor. That stability and sense of resolution are why the tonic functions as the key’s anchor. The other descriptions don’t fit: the subdominant pitch would give the IV chord, not the tonic; the tonic triad is indeed diatonic; and the tonic is the most stable, not the most unstable, chord in the key.