The three forms are made from panels of alloyed bronze. Each panel was produced individually by pouring the molten metal onto two kinds of surface: bare concrete or stainless steel. Gases escaping from the materials formed irregularities in the color and texture of the panels, which are themselves individually sized. The results look like travertine marble alchemically rendered into bronze. (Compared with this radiant effect, the marble miracle mile of the Getty Center in Los Angeles looks produced by reverse alchemy. Travertine in, chip board out.)

The architects have acknowledged that the form created by the triangle atop the window is an etherealized human hand. The image establishes the building in relationship to the craft tradition and also to the continuity of modernism as epitomized by the French architect Le Corbusier. That 20th-century pioneer inscribed hand forms into his poured-concrete buildings to symbolize humanity's mastery of tools. This is the common theme Mr. Williams and Ms. Tsien have uncovered for their building and the art inside it.

The museum's interior is an atrium of domestic proportions, slightly stretched. Even without a fireplace and rum punch, the place is companionable. The intimacy is also an alchemical operation, because visitors will be moving around and atop the building's exposed concrete structure. At first you may not notice this Brutalist proposition. In the galleries the concrete has been polished to reveal the terrazzolike aggregate within it. The 19th-century philosophy of ''truth to materials'' is applied more consistently here than in buildings by Frank Lloyd Wright.

Most of the art is displayed in a compact stack of four gallery floors that rise from the second story to a skylight on the roof. Elevators serve the galleries, but staircases offer a better way to experience the spatial continuity. A wide main staircase is complemented by narrower flights along the side walls. Designed on the scale of backstairs in a mansion, the latter encourage visitors to find individual paths through the museum.

The arrangement of galleries recalls Mr. Williams and Ms. Tsien's design for an art collector's private house in Manhattan, completed in 1995. Low-ceiling spaces of roughly rectangular shape alternate with longer balcony areas overlooking the central atrium. What is the opposite of museum fatigue? This arrangement embodies it.

A giant weathervane of yellow metal dominates the atrium's thin slot of a void. Designed in the form of a Native American chief, this haunting figure is pierced by bullet holes made by the American pastime target practice, a post-tavern amusement, perhaps. The weathervane dominates the space not only by virtue of scale, but also by suggesting that the museum's view of folk art is not naïve. Folks can be quite mad. As both cowboy and Indian, Charlton Heston is folk art, too.