Head voice
A high vocal register felt to resonate mainly in the head.
What it means
Head voice denotes a high register of the human voice in which the vocal folds vibrate only partially and the resonance is felt mainly in the head rather than the chest. The sound is typically lighter and brighter than in lower registers.
Musical use
Head voice is contrasted with chest voice, produced lower down with fuller vocal-fold involvement and perceptible resonance in the chest; the transition between the two is called the register break or passaggio. Trained singers smooth this transition using a mixed register (middle voice), so the change stays as inaudible as possible. In male voices, a particularly light, often flute-like use of pure head voice is also called falsetto, while female voices generally use head voice as a natural high register without a separate name.
Performance practice
Practise the transition between chest and head voice slowly and with little pressure; don't force the register change, but look for the point where the two colors can blend rather than flipping abruptly.