Expression Pedals are used by the organist to manipulate the adjustable louvers or Swell Shades with which enclosed divisions of the organ are provided.

Expression Pedals are used by the organist to manipulate the adjustable louvers or Swell Shades with which enclosed divisions of the organ are provided.Pedals used by the organist to manipulate the adjustable louvers or Swell Shades with which enclosed divisions of the organ are provided. The shades increase or decrease the volume, enabling the organist to give expression to the division or to adjust the volume of solo stops.