1
general::
Say or do what is especially appropriate, as in She struck the right note when she complimented the new parents on their baby. This expression alludes to playing the correct note on an instrument.
American Heritage Idioms
2
general::
Phrase(s): strike the right note
Fig. to achieve the desired effect; to do something suitable or pleasing. • Meg struck the right note when she wore a dark suit to the interview. • The politician’s speech failed to strike the right note with the crowd.
McGrawhill's American Idioms And Phrasal Verbs