This article investigates jazz play-along recordings as a distinct media form that reshaped pedagogical practice and temporal experience in jazz education. Drawing on sound studies and media archaeology, the study examines how this ubiquitous technology creates what I term "play-along time"—a mode of musical temporality fundamentally different from live combo interaction (Gitelman, 2006; Ihde, 2012).The research addresses three questions: How do play-alongs differ from live jazz performance? How might these differences be consequential for learning? What implications emerge for pedagogical practice? Theoretically, the work builds on scholarship examining educational simulations and technological mediation in music learning, while drawing from phenomenological accounts of temporal experience in performance (Miller, 2012).Methodologically, this media-archaeological study combines oral history interviews with musicians who created early play-along tracks and comparative audio analysis of original recordings versus their play-along counterparts to develop a phenomenological account of play-along time (Zielinski, 2006). The historical investigation traces the play-along's prehistory from the earliest play-along recordings of the 1930s through pedagogical practices of comping for student soloists that connect to commercial series in the 1960s-70s.Oral history interviews with over a dozen jazz artists involved in the creation of Play-A-Long recordings reveals that session musicians struggled to "accompany nobody"—often requiring a "ghost soloist" in headphones, later erased, to make recordings feel authentic. Comparative sound analysis of recordings by identical musicians reveals measurable differences: play-along time exhibits greater temporal stability, reduced interactive density, and altered figure-ground relationships. Rather than the reciprocal contingency of live performance, play-along time creates one-way temporal flow from deliberately restrained rhythm sections outward to absent (future) soloists.Results demonstrate how this media form foregrounded music theory through theory-only tracks dispensing with melody entirely, recalibrating jazz's balance between theoretical logic and interactive spontaneity. The genealogy extends from early commercial series through iRealPro and Band-in-a-Box to contemporary AI-generated backing tracks, suggesting play-along time has become naturalized in how improvisers learn.For music education, findings suggest play-alongs offer specific affordances (accessible practice tools, theoretical focus) while constraining others (responsive interaction, contingent time-feel). The study concludes that educators should understand play-alongs as pedagogically useful simulations rather than substitutes for live performance, recognizing how their temporal characteristics shape student experience. As mediated practice environments proliferate, critical awareness of their material conditions becomes essential for developing pedagogies balancing technological affordances with interactive traditions central to jazz practice (Ake, 2002; Prouty, 2023).