“Building for richness” is an ideal that means building a combination of stops that is intended to produce a full, warm ensemble. This moves away from the ideal of “building for clarity,” although some degree of clarity is nearly always musically desirable.
Central to building for richness is pitch duplication, where more than one stop is used at some pitch. Using this method, BUILD OUTWARD first (see stops in blue squares to the right), before building upward (see stops in yellow rectangle to the right).
Building outward is a PYRAMID-like method of registration. Using this method, there are always more stops pulled at the lower pitch levels. If there is one 4' stop, there are two 8' stops (see green triangles or pyramids to the right); if there is one 2' stop, there are three 8' stops and two 4' stops (see black triangle or pyramid above and to the right).