Weighted Keys. If you've played an acoustic piano, you've played on weighted keys. Weighted keys also exist on digital pianos and keyboards in two varieties — semi-weighted and fully-weighted. Semi-weighted keyboards have a uniform amount of resistance across the whole keyboard. The key word for semi weighted is uniform amount of resistance.
One feature of a touch sensitive keyboard is being able to play some keys louder than other keys such as a melody along with harmony. Being able to play the melody louder.
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.
Most likely your Allen might at best have a touch sensitive feature or possibly none of the above.
Another feature on theatre organs is second touch where unless you press down on one or more keys harder than normal, the keyboard functions as do the keyboards without this feature.
Second touch (2T) is a feature of keyboard and pedalboards that activates a second set of contacts when the key is pushed with a bit more pressure. On a Wurlitzer the manual keys move about 1/8 inch further down past the first touch position.
Second touch stops are provided for each manual that has the second touch feature. On Wurlitzer theatre organs, the bottom two manuals and the pedals have second touch. Therefore both manuals and the pedals have second touch on the style 216. Wurlitzer second touch stops are shorter and located on the straight fall board immediately behind the upper manual. Percussions are many times played by pushing down keys already being played just a bit more to activate these.
As far as which is best for an organ, weighted or semi weighted are not generally used. It depends on a preference beyond that.
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