The Crowd, executed around 1920-21, is one of Tack's most dynamic, abstract compositions at this point in his career; it is composed of human and landscape forms inextricably linked in swirling movement and liberated color. The image forecasts the gradual suppression of the figure in the landscape themes of Tack’s later work. The painting also served as the basis for Tack’s landscape series painted over the next few years as well as the Music Room series commissioned by Duncan Phillips for his museum in 1928.
To create this vortex of figures in motion, Tack drew from a myriad of sources; the painting indicates that Tack was interested in a broad range of artistic movements. The Crowd looks both backward to his interest in the old masters, such as the entangled figures in Renaissance depictions of The Last Judgment and related themes, as well as japoniste design, and forward to experiments with pure color, rhythmic formal harmonies, and fresh explorations of nature. A characteristic love of japoniste design is betrayed in the two-dimensional arrangement and the ambiguous figure-ground relationships. Furthermore, in The Crowd, Tack employed a non-hierarchical pictorial construction reminiscent of cubism and revealed his awareness of cubo-futurist vocabulary through his use of force lines and reductive, geometric simplification.
Tack's use of many perspective points and a structure that seems to have no clear order creates an image of anarchy and chaos with clear moral undertones. The figures, posing in various attitudes of despair, worship, supplication, and fear, are allegorical; those on the right side appear in poses of prayer, while those on the left seem agitated and tormented. Beginning with this painting, the creation of order from chaos as well as the cycle of sacrifice, destruction, and ultimate redemption are the dominant themes of Tack's abstractions.
Tack built up the picture with a collage-like combination of techniques, including stenciling, transfer of drawings or photographs, and freehand painting. The sky was first painted light blue, then beige with cerulean accents over a coat of varnish. The entire work, including the aluminum-leafed frame, was distressed with rollers and cloths, conveying the antique refinement characteristic of Tack's Beaux-Arts training and his love of texture.
Duncan Phillips praised this work as "a powerful and personal abstraction and unique in [Tack's] own work," and a "miracle of turbulent movement." In general, The Crowd was singled out as a highly successful work and praised for its colorful spirit.