A grand piano is a type of piano in which the cast metal frame, metal strings, and thin wooden soundboard are are all positioned horizontally, with the strings extending away from the keyboard, in contrast to upright pianos, in which the frame, strings and soundboard are vertical. When a player presses a key on a grand piano, the corresponding hammer strikes the strings from below and returns to its resting position by gravity. This mechanism is thus less subject to degradation than the spring mechanisms in upright pianos, and it also results in a crisper sound for repeated notes. In addition to improved responsiveness and better control of the sound, grand pianos can also create a greater volume, especially when their top is raised, because they emit sound from above rather than from their rear. This makes them, especially the largest models, well suited for concert halls and other large spaces.
Grand pianos are produced in three standard sizes, ranging in length from approximately 1.5 meters to 3 meters: baby grand, parlor grand, and concert grand. Longer grand pianos with longer strings produce sound that is richer and more pure and that can have a larger volume than those with shorter strings.