Of speech, to have or communicate a certain kind of tone or attitude. The president struck an beleaguered note in his address to congress, as he tried to convince them to vote for the healthcare bill he is backing. The manager struck a rather insincere note as he expressed his sorrow at the round of layoffs.

To indicate, introduce, or allude to something particularly unfortunate, unpleasant, or disagreeable. You definitely struck a sour note when you brought up Dan's ex-girlfriends during your best man speech.