Wiktionary
n. 1 (context music English) The highest and usually climactic note of a song or composition, especially one that is difficult to reach. 2 (context figuratively idiomatic English) Something's climax or best achievement. 3 (&lit high note English)
Wikipedia
High Note is a Warner Bros. Looney Tunes animated short directed by Chuck Jones. It was originally released on December 3, 1960 and is performed without dialog, relying solely on the animation and music to carry the plot. This short was nominated for an Academy Award for Best Short Film (Cartoon) in 1961.
Usage examples of "high note".
But Isler was no Saganami, and the sharp, high note of panic in his voice as he gabbled incoherent orders over the command net finished any hint of cohesiveness in his shattered force.
In five minutes the dull noise of the curbstone market in Broad Street had leapt to a high note of frantic interrogation.
The bird sang again, a quick, high note that was so pure and true she almost cried at the sound.
Without even knowing it, we are assaulted by a high note of urgency all the time.
His name ended on a high note as his finger traced a circle on her bosom.