This refers to the expansive wooden surface beneath a grand piano’s strings. It is integral to the overall sound of the piano. Essentially, it fulfills the same function as the body of a violin or acoustic guitar and is connected to the strings in a similar fashion, i.e., the strings press up against a bridge which is attached to the soundboard. Wooden braces are used to reinforce the soundboard and are carefully placed so they do not affect the overall tone. In the finest pianos, there is a slight arch to the soundboard, just as there is in a violin or archtop guitar. Budget-priced grand pianos usually have a flat soundboard.