In the second movement Cage brings the piano under the control of a second, parallel but distinct chart, creating an increasing sense of confluence between the soloist and the ensemble. The final movement is one of the great revelations of Cage's oeuvre. In the extraordinary third movement these two governing systems both reach their apotheosis. The prepared piano is brought under the control of the same chart which guides the orchestra, releasing it from the hunger for self-expression. In the Concerto for Prepared Piano and Chamber Orchestra , Cage, in stripping away the sounds of the piece and reducing it to silence, shows us the heart of the music.
Form is shown to indeed be emptiness.
As Cage's artistic journey continued, silence became a starting point, a governing principle, a trademark or leitmotif. In his final compositions, the extreme sparseness of the written music takes on a dramatic, almost shocking character. In this world a single sound is a major event, and the luminescent immobility of the sustained tones becomes a metaphor for the stillness of death. Dynamics are left to the players' discretion with the understanding that loud sounds will be short. Except for the piano solo, the parts are missing several time brackets, yielding long stretches of silence from individual players and unpredictable variations of texture.