Pipe organs are extremely practical and existed in Greece and Byzantium BC.
A tracker organ could not be simpler. You need air under pressure, a wind chest, pipes on top of it, which are in essence whistles, and sliders with holes in x/y graph format. The sliders have holes. The keys are on the x axis, and the stops on the y. When an x and y hole line up a pipe sounds. It could not be simpler and it is very practical. That is all there is to it. The rest is craftsmanship.