Which term is used to describe two keys that share the same tonic note?

The term that describes two keys sharing the same tonic note is "parallel keys." This concept refers to major and minor keys that have the same root note, but different modes. For example, C major and C minor are considered parallel because they both begin on the tonic of C but differ in their scale structure and mood.

Relative keys, on the other hand, refer to pairs of keys (one major and one minor) that are related by their key signature but have different tonic notes. For instance, C major and A minor are relative keys; they share the same key signature but have different tonics.

Harmonic keys is not a standard term used to describe key relationships, and chromatic keys typically refer to the use of chromatic notes, rather than a relationship between keys.

Thus, parallel keys is the correct response because it specifically emphasizes the shared tonic note characteristic.