GarageBand Piano
The Piano instrument is sample based. It emulates a number of classical and jazz piano sounds. It also emulates several accordions and a harpsichord, and it provides a number of pad sounds.
Volume slider: Sets the overall volume level of the instrument.
Filter Cutoff slider: Allows more (high) or less (low) of the sound through, making it brighter or damping it.
Release slider: Determines the time it takes for notes to fade out after you let go of the keys on your keyboard.