high note

/HH AY1 N OW0 T/
noun
  1. 1

    The highest and usually climactic note of a song or composition, especially one that is difficult to reach.

    โ€œAfter weeks of practice Alyssa was finally able to hit the high note of her song perfectly.โ€

  2. 2

    A climax or best achievement.

Source: https://en.wiktionary.org/wiki/high%20note