A key for a keyboard instrument, which makes it possible to easily attach a weight to a synthetic resin-made key body while securing a desired touch weight to be given during key depression, and can be manufactured at low costs. The at least one alignment block is for aligning serial input data into groups of parallel data synchronized to at least one divided data strobe signal for increasing margin between the maximum and minimum tDQSS values. A plurality of waistband fasteners are spaced apart along a waistband outer surface, each waistband fastener having a configuration complementary a waistband coupling member for selective attachment thereto. A corresponding method is also described. According to requirements to change the electrical polarity of the common electrode, a control unit in the driving circuit turns onoff the two switches respectively so as to charge or discharge the AC voltage output terminal.