Upright pianos, also called vertical pianos, are more compact because the frame and strings are vertical, extending up and down from the keyboard and hammers. It is considered harder to produce a sensitive piano action when the hammers move horizontally, as the vertical hammer return is dependent on springs which are prone to wear and tear. The grand piano hammers return by gravity, hence they will always return more consistently than the vertical hammers, thus giving pianists better control of their playing. However, a well-regulated vertical piano will probably play more smoothly than a grand piano that has not been regulated for years, and the very best upright pianos now approach the level of some grand pianos of the same size in tone quality and responsiveness.
One noticeable advantage that the grand piano action has over the vertical action is that all grand pianos have a special repetition lever in the playing action that is absent in all verticals. This repetition lever, a separate one for every key, catches the hammer close to the strings as long as the keys are played repeatedly and fairly quickly. In this position, with the hammer resting on the lever, a pianist can play repeated notes, staccato, and trills with much more speed and control than is possible on a vertical piano.
Another type of upright, is a combination of all 3 types of pianos. It is called an upright grand player piano, and has many features of both instruments. Though rarely heard or seen of, grand upright pianos have their strings set differently than regular uprights. As all uprights do, the strings are set "upright" to play. With the grand style of this piano, the strings are longer, making the piano bigger. While the dimensions of width and length remain the same, it is the height that is considerably different. Upright pianos are usually a little more than 4 feet tall, while upright grands are usually around 5'5" or so. The longer strings allow the piano to have a richer sound and, if made of wood, create a nice warm tone in both the bass and treble. The player piano part takes the idea of the roll and fits it into the piano, much like any other piano. The controls are always hidden. In some pianos, the control for tempo is in the wooden beam in from of the keys, the roll itself hidden by a wood curtain in front, and the pedals hidden by a wood curtain on the bottom. By now, most of these pianos are rare, and if they are found, may be in unplayable conditions. Some are over 100 years old now.
