Whistle register

The whistle register (also called the flageolet register and in Speech Level Singing the super-head register) is the highest register of the human voice. The register is so called because the timbre of the notes that are produced from this register is similar to that of a whistle.

Physiology and definition
The physiology of the whistle register is the least understood of the vocal registers. It is known that when producing pitches in this register, vibration occurs only in some anterior portion of the vocal folds. This shorter vibrating length naturally allows for easier production of high pitches. The physiological process that causes this is not currently known.

The whistle register is most commonly used to produce pitches around and above the soprano C. By the physiological definition just detailed, it is a configuration of the vocal folds and is a range of pitches. However, there is no universally agreed-upon scheme for classifying vocal registers, so it is common to see other definitions.

Uses of the whistle register
In European classical music, the whistle register is rarely called for. When it is, it is exclusively used by coloratura sopranos to produce pitches above C6. Probably the best-known example of the whistle register in European classical music is in the "Queen of the Night" aria (properly titled "Der Hölle Rache kocht in meinem Herzen") from the Mozart opera Die Zauberflöte; it calls for pitches up to F6.

In Western popular music, the whistle register is used with more variety and to produce much higher pitches than are called for in classical music. While it is mostly used by females, such as Mariah Carey and Minnie Riperton, there are a few male singers who use it. Georgia Brown holds the record for highest note ever reached. Among male singers, the one who holds the Guinness Book of Records record (C#8) for highest vocal note by a male, Adam Lopez, makes extensive use of the whistle register.