Song Books (1970) is a remarkably diverse collection of 90 musical and theatrical pieces that encompasses over 50 compositional techniques. Several pieces refer back to Cage's earlier works, notably Aria, Concert for Piano and Orchestra, Winter Music, and 0'00", whereas others introduce new methods. Some of the “songs,” all titled “solo for voice,” are fixed scores that call for singing. But many others do not necessarily involve vocalization at all; instead they give directions for various actions—preparing food, eating, drinking, writing—or for constructing pieces based on what appear to be random arrangements of words or numbers. Half of the solos are to be performed with mostly unspecified electronics (though often with detailed directions for how to employ them), and each is labeled as either relevant or irrelevant to Cage's theme for Song Books: “We connect Satie with Thoreau.” In some solos, Cage composes “cheap imitations” by retaining the rhythms of pieces by Satie, Mozart, Schubert, or others but randomly altering their pitches. In another, the performer is directed to compose a melodic line by tracing a portrait of Thoreau, or by traveling from one point to another on a map of Concord, Massachusetts. Still other solos call for producing feedback, projecting slides, playing a recording of a forest fire, typing a sentence 38 times on a highly amplified typewriter, or simply entering and leaving the stage. Song Books is inherently enigmatic and interdisciplinary, blurring boundaries among art forms and raising questions about the nature of performance.

Like many of Cage’s works, Song Books is indeterminate with regard to performance, though once plans for a performance are made, they are to be followed rigorously. Any number of performers are to decide on a duration for the entire rendition, select pieces from among the 90, and determine their order—typically independently, without knowing what the other performers will do. Any solo may be performed in whole or in part. The score suggests no particular form, narrative, or dramatic curve. Moreover, a performance of Song Books, or some of its solos, may include other compositions that feature indeterminacy, or incorporate other optional sounds. Such an “open” structure might seem to leave Cage’s work prone to chaos or at least misinterpretation, yet the composer expected it to be prepared with great care and discipline, and objected adamantly to improvised renditions or those that unduly emphasized performers’ egos. The work's social and political overtones—fostering freedom yet with discipline, participation yet without interference—are as relevant today as they were in the milieu of 1970. Song Books' purposeful ambiguity has inspired a wide range of interpretations from the understated and elegant to the spectacular and hilarious. Its myriad opportunities for experimental and multi-disciplinary art-making abundantly evoke, to paraphrase Cage, "joy and bewilderment," for performers and observers alike.