1) Pipe organ component 
Photographic images made with microscopes. ... Tracker action is a term used in reference to pipe organs and steam calliopes to indicate a mechanical linkage between keys or pedals pressed by the organist and the valve that allows air to flow into pipe(s) of the corresponding note. This is in contrast to `direct electric action` and `electro-pneumatic action`, which connect the key to the ...
in music, on the organ, mechanical system that transmits the organist`s action in depressing a key to the pallet valve that admits air into the ... [1 related articles]