What are whistle notes?

Whistle notes are extremely high-pitched vocal sounds produced by singers, typically in the upper register of their range. They are often characterized by their clarity and brightness, resembling a whistle, hence the name. These notes are usually achieved by using a specialized technique that involves adjusting the vocal folds and resonating cavities. Whistle notes are commonly found in various musical genres, particularly in pop and Opera, showcasing a singer's vocal agility and range.