The action of an organ admits either wind to a pipe (key action) or controls which ranks are engaged (stop action). So an organ contains two actions, or systems of moving parts. An action may be mechanical, pneumatic, or electrical. The pneumatic action was invented during the Romanesque period. Compared to the mechanical action it allowed a greater distance between the console and the wind chest, larger ranks and different registration aids. Disadvantages are the delay between pressing a key and response of the pipe, bad maintenance (leaking) and missing touch of the keys.
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