Tracker action

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 valve through an electrical link or an electrically assisted pneumatic system respectively, or "tubular-pneumatic action" which utilizes a change of pressure within lead tubing which connects the key to the valve pneumatic.

History

Ancient history

Organs trace their history as far back as at least the 3rd Century B.C. with an organlike device known as the hydraulis. Also known as a "water organ" or "Roman organ," the Hydraulis was an instrument in which water was used as a source of power to push wind through organ pipes. (It is not to be confused with the hydraulic action of a hydraulophone, an instrument that actually uses water to produce the sound, not just as a source of power). While the control of air pressure was controlled by water pressure, hence the name, the action was a rudimentary form of modern action.