A vocal harmonizer is an electronic device or software that enhances vocal performances by adding harmonies to a singer's voice. It works by analyzing the pitch of the input voice and generating additional notes that complement the original melody. This technology is commonly used in music production, live performances, and recording studios to create richer and fuller vocal sounds. Vocal harmonizers can be found in various forms, including hardware units and digital plugins. They are often used by musicians, producers, and sound engineers to achieve professional-sounding results. Popular examples of vocal harmonizers include products from brands like TC Helicon and Eventide.