Steve Reich’s minimalist composition Different Trains (1988) for string quartet and tape uses the speech prosody of recorded testimony as its fundamental melodic material. This article adapts Peircean semiotics to explore how Reich’s co-constituting treatments of recorded voices—as testimonial evidence and as musical melody—create two co-constituting operations that make possible Different Trains’ meaning-making capacity. First, the taped voices’ isolation and reproduction complicate the function of language as a set of stipulated symbols by refiguring the speech fragments as material and indexical traces of testimony, not the testimony itself. Second, the transformation of these prosodic fragments into gestural melodies makes the voice’s intonational curve an iconic gesture requiring an attentive, even participatory, listening practice. The two operations work in conjunction toward a representation not of history itself, but of history’s recurring and highly mediated experience within the present. The intermedial network of sign systems in Different Trains is made possible through Reich’s implementation of sound technology in composition and performance. Careful attention to the work reveals the extent to which word and music studies are complicated when the material conditions and acoustic interventions of aural media are taken into account.