Keyboard scaling is a parameter found in many modern keyboards. Its function is to provide a way for a sound to be altered smoothly across the range of the keyboard. This is accomplished by using the key number as a modulation source and routing it to some parameter the user wishes to alter. Level scaling changes the loudness of the sound, while filter scaling changes its brightness. In some synthesizers key scaling can be routed to many parameters simultaneously with different strengths and polarities. The practical application comes out of programmers trying to make acoustic type sounds more realistic across the entire range of the keyboard.