The piano is classified in orchestras as a percussion instrument. However, it can be classified more of a hybrid between strings and percussion. It's played by pressing a key which triggers a hammer to hit a string which causes the sound. The note is changed when the player either goes right or left on the keyboard. When the player desires to play a higher note, they would press a key to the left and vice versa. Pianos either come in the upright position or the regular landscape position. Upright pianos are usually rectangular/square shaped while grand pianos (landscape position) are usually curved at the end, with the lower notes having protrusion. The piano's strings have different thicknesses and lengths which help to create the sound. Generally, the lower notes are played by thicker and longer strings while the higher notes are played by not as thick, and shorter strings. 

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