Video narration
What changes inside your throat when your voice moves from low to high? Think of a rubber band: pluck it when it's stretched tighter, and it makes a higher sound. That's a useful comparison, though vocal folds aren't rubber bands. Your vocal folds are two small folds of tissue in your throat. Air from your lungs sets them vibrating, and the speed of that vibration is what you hear as pitch. Faster vibrations sound higher; slower ones sound lower. Here's the key: high notes don't come simply from pushing more air. Your vocal folds change shape, and that changes how quickly they vibrate. As they stretch thinner, they vibrate faster; as they become shorter and thicker, they vibrate more slowly. That's what changes inside your throat: faster-fold vibration gives you a higher pitch, slower vibration a lower one.