Since the middle of the 20th century it has become common in rock and later all forms of pop music to regularly to play non stressed beats in a percussive way – often by slaps – or to emphasize it dynamically. Particularly in the vastly popular 4/4 measure, the 2nd and 4th beat are emphasized in this way against the „natural“ emphasis (see shuffle), while the 1st and 3rd beat, on the other hand, are held off.