Metamorphosis, a solo piano work in five sections, takes its name from Kafka's famous short story. While the third and fourth sections were composed as incidental music for theatrical portrayals of the man-turned-bug, the first two sections borrow themes from music Glass composed for a different story of metamorphosis—the tale of man-turned-murderer from Errol Morris' 1988 documentary, The Thin Blue Line. Glass later composed the final section specifically as a conclusion for the grouping.

In each movement, the music does not depict the actual change of state, but rather a reflection upon it and, perhaps, a sense of resignation. Glass' music, free of electronic accoutrements, amplification, and ensemble concerns, is strikingly intimate, and provides a haunting backdrop for both tales. The 1989 CBS recording (MK 45576) features the composer's own performance of the work.

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