in key
In consonance or accordance with other elements, factors, or styles. A reference to musical tonality. Jonathan's fashion sense is impeccable, with each facet of his ensemble in key with the others.
in key
In harmony with other factors, in a matching style, as in This furniture is perfectly in key with the overall design. This term uses key in the musical sense, that is, "a scheme of notes related to one another." The antonym, out of key, means "not in harmony with other factors," or "unsuitable," as in He is out of key with his time. [c. 1900]
in (or out of) key
in (or out of) harmony. in key
In consonance with other factors.