I. ˈkē-ˌnōt noun
Date: 1776
1. : the first and harmonically fundamental tone of a scale
2. : the fundamental or central fact, idea, or mood
sadness is the keynote of this little collection — Books Abroad
II. transitive verb
Date: 1914
1. : to set the keynote of
2. : to deliver the keynote address at
• key·not·er noun