The American Piano Company, in the early twentieth century, built a reenacting piano that could automatically play back performances recorded by virtuoso pianists. This article examines the production, in the company lab, of that piano’s fidelity—the terms by which an original and reenacted performance could be said to be the same. Taking fidelity not as an objective measure of sameness but rather as a mediation between machinery and people, the author finds in the discourse around the re-enacting piano echoes of the nineteenth-century scientific “mechanical objectivity” identified by Lorraine Daston and Peter Galison. The re-enacting piano’s “mechanical fidelity” was developed in the laboratory and advertising copy as a conjunction of objectivity, materiality, and identity. Through a commingling of traits that had formerly been considered either human or mechanical, the re-enacting piano offered a way to imagine human and machine performances as materially interchangeable and potentially identical. Human and mechanical identity are mediated through the details of fidelity, and this article argues that by exploring the production of a fidelity quite unlike the phonographic fidelity that would come to define the word, we can better understand the contingencies of reproducing technologies and the human identities—including our sense of sound—that are shaped in collaboration with them.