Second-hand pedalboards fitted with contacts, which are connected to a small electronic unit, that produces midi signals on any one channel (channel to be specified by the user). This enables the pedalboard to be plugged in to any standard keyboard (most keyboards manufactured in the last ten years or so have midi inputs) and play a sound from that keyboard. The unit can normally be programmed to select any sound of your choice for the pedalboard, on switch on. You can then manually select a different sound to play on the keyboard.
Alternatively they can be used with a computer via a suitable midi interface. This enables them to be used with Hauptwerk, Prog Organ and other virtual organ programs.
By fashioning a suitable stand and bench, a single manual organ can be made in this way for very low cost. Price is around £350 depending on the quality of the pedalboard. If benches are available, these are £50 to £100. New keyboard stands with a solid wood top, adjustable in height and wide enough to straddle the pedalboard cost £150.