George Crumb completed Celestial Mechanics, Makrokosmos IV: Cosmic Dances for Amplified Piano, Four-Hands in 1979. The Makrokosmos series began in 1972 with a work for solo amplified piano featuring twelve movements that were named after the signs of the zodiac. In 1973, the composer created a companion piece to Makrokosmos I that was basically a variation on the same design as the first. These two works form a homage to Debussy's 24 Preludes, which was also in two parts. Makrokosmos III appeared in 1974 and was scored for two amplified pianos and percussion, emerging as one of the best-received avant-garde chamber works from the second half of the twentieth century. All these pieces had a common theme of cosmic design, alluding to a large and mystic outlook that seems unique to the composer. All three of these works have a deep, American dreaminess, even impressionism, that draws few, if any comparisons. Makrokosmos IV is less cerebral than its forerunners, featuring terse rhythms with a tactile edge. With this piece, Crumb is also reflecting on his love of the four-hands works by Mozart and Brahms, as well as the fantasy and dance genres. He equated the term fantasy with the cosmos, and hence came upon an approach to a piano suite that would extend the Makrokosmos series. The term "Makrokosmos" comes in response to the Microcosmos series by Bartók, which illustrated his compositional directions in six volumes for solo piano. Crumb took it further to include extended techniques and electro-acoustics, creating a series that stands as a brilliant addition to the chamber music catalog.

Celestial Mechanics is in four movements, and is slightly more than twenty-one minutes in duration. It features some of his densest textures, generating sparkling, crackling rhythms with tremendous life. In keeping with the spirit of the series, each movement is titled after the names of stars. Crumb referred to a "cosmic choreography" that such a collection of celestial dances might entail. There is a broad compass of energy demonstrated in this work. The final movement contains the least fireworks, concluding with a set of static chords that round out the dances with a sublime release. It also contains, as does the third movement, moments when the page-turner is also obliged to contribute, so that the four-hands work is briefly enlarged to six-hands. This innovation expands the breadth of contrasts in the work, giving it almost orchestral proportions. Though the work goes from hair-raising speeds to utterly languid evocations of nocturnal Americana, there is little ebb and flow in the work's overall energy. The language of the music works on a constant level so that the contrasts have a continuous, extra-rhythmic integrity. In not too many words, it is not the music that begs the listener to be agitated at one moment and then relaxed in another, though the piece's surface would suggest exactly that. It is all one fabric, featuring a surface that generates a kaleidoscope of ways to hear the same, extended structure, which features one greater, universal rhythm. In that way it reflects the heavens and the celestial bodies that are constantly referenced in his music; stars that do not speed up or slow down. Throughout his career, Crumb has made these sorts of insights regarding the cosmos a part of his works. If it is part of any specific belief system that extends beyond the composer himself is difficult to determine. It demonstrates warmth and curiosity, as well as a love of life that touches even the most casual listener. Celestial Mechanics is the final chapter of the haunting yet magnificent Makrokosmos series.

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