D defs.my
Entry 2 senses Webster, 1913

Keynote

/kēn'-ōtˌ/ · Key·note · IPA /ˈkiːˌnoʊt/
01 n. The tonic or first tone of the scale in which a piece or passage is written; the fundamental tone of the chord, to which all the modulation…
  1. 1.
    The tonic or first tone of the scale in which a piece or passage is written; the fundamental tone of the chord, to which all the modulations of the piece are referred; -- called also key tone.(Mus.) Also: key tone
  2. 2.
    The fundamental fact or idea; that which gives the key; as, the keynote of a policy or a sermon.