Piano mechanisms: upright vs grand
In an upright piano, the strings are positioned vertically on the frame whereas the strings on a grand piano are horizontal. The hammers in an upright piano are pushed forward to strike the strings, with springs to return them to their rest position once the note has been played. This mechanism enables a reasonably quick repetition, of up to 7 times per second. However, as the hammers in a grand piano are forced upwards to strike the strings and return downwards under their own weight, repetition is much faster and more accurate, with a possible repetition speed of up to 14 times per second.