Grand pianos have the frame and strings placed horizontally, with the strings extending away from the keyboard. This makes the grand piano a large instrument, for which the ideal setting is a spacious room with high ceilings for proper resonance. There are several sizes of grand piano. Manufacturers and models vary, but a rough generalization distinguishes the "concert grand" (between about 2.2 m to 3 m long) from the "parlor grand" (about 1.7 m to 2.2 m) and the smaller "baby grand" (which may be shorter than it is wide).
A relatively recent development is the prepared piano, which is used in contemporary art music. A prepared piano is a standard grand piano which has had objects placed inside it before a performance in order to alter its sound, or which has had its mechanism changed in some way. The scores for music for prepared piano often instruct the pianist to insert pieces of rubber or small pieces of metal (screws or washers) in between the strings. These added items either mute the strings or create unusual vibrating sounds.
