In the 1920s, Tack began his most daring explorations in abstraction, works that united tradition and modernism in a striking manner. Several trips to Europe in the 1920s awakened a deep interest in mosaics and the paintings of Giotto, whose works informed Tack’s figurative and abstract work. A Biblical symbolism inspired the central themes of some of his abstract works. Tack achieved a remarkable grandeur and subtlety in the series of paintings he produced between about 1922 and 1924. Their formats draw on decorative and Renaissance sources, such as in this work, Passacaglia, where he adopts a tondo (circular) format derived from European decorative traditions. While Passacaglia is the only work devoid of overt religious content, the work’s preparatory sketch depicts the holy family in a scene from the Nativity, suggesting its Biblical origins.
Tack began with New Testament subjects and gradually turned to more universal evocations of matter and spirit. Similar to other works of the early 1920s, the composition highlights dynamism and movement, fragmentation of forms in space, and rhythmic repetitions appropriate to its theme, as Passacaglia was titled after a medieval Italian street dance that was later adapted as a movement in Baroque music. One of Tack’s most complex, ambitious, and fresh creations, Passacaglia dancing figures create a pulsating, swirling movement that is enhanced by the circular format.
The western terrain found its way into Tack’s imagery in the 1922-24 paintings. Tack's first view of the Rocky Mountains in the summer of 1920 permanently reoriented his approach to painting. Nineteenth-century painters had romanticized the Western landscape; many later American artists sought to capture the majestic scenery of the West in highly personal terms. In the West, the artist could infuse the natural grandeur with implications of a broader spiritual and philosophical meaning—an approach Tack adopted in the dematerialized shapes and fragmentary mountain forms of Passacaglia.