Slider (organ)
A movable strip of wood in an organ's wind chest that opens or blocks wind to a stop's pipes.
What it means
The slider is a narrow, ruler-like strip of wood in an organ's wind chest, perforated with holes, that can be pushed back and forth beneath the feet of the pipes belonging to one stop.
When a hole in the slider aligns with a pipe's foot, wind can flow to it; when the slider is shifted, the solid wood between the holes blocks the wind supply to the entire rank of pipes in that stop.
Musical use
The slider is moved by the stop knob that the organist pulls or pushes at the console; it therefore does not control individual notes but switches an entire stop — a single timbre across the whole range — on or off.
The slider gives its name to the slider chest, the most widespread historical and still most commonly built type of wind chest, in which each stop has its own slider, while note selection within a stop is handled by separate valves under each key.
The slider should be distinguished from the cone chest and the tubular wind chest, in which other mechanical or pneumatic devices handle both note and stop selection, without using a continuous, movable strip like the slider.
Performance practice
Pull a stop all the way before playing its keys, since a slider only half drawn can cause uneven speech or no sound at all. Plan stop changes within a piece so there is enough time to operate the controls cleanly.