Public music participation in everyday spaces remains unevenly accessible, particularly for people without formal performance opportunities. Drawing on informal learning and theories of proxemics, affordances, and choice architecture, this study tests whether simple spatial cues invite active playing in a real public setting. We conducted a field quasi-experiment manipulating the placement (center versus wall-adjacent) and the orientation (front-facing versus back-facing relative to the predominant pedestrian flow) of a freely accessible digital piano in a single atrium, yielding a 2×2 design. Across all conditions, an identical informational and welcoming notice was displayed to meet minimal-risk ethics and avoid confounds. The study asked whether these spatial cues change (a) the probability that passers-by start to play (participation rate), (b) playing duration among those who engage, and (c) the number of bystanders and their approximate dwell time. Conditions were rotated across comparable time slots, counterbalanced by day and time of day. Trained observers recorded anonymous behavioral outcomes on standardized sheets: active playing events (physical contact with keys for ≥5 s), event duration, bystander counts within approximately 2-3 m, and binned dwell time. No personal or identifying data were collected; venue permission was obtained. We report preliminary findings from the ongoing pilot together with the full, replicable protocol for use in schools, campuses, libraries, and community venues. The study offers a low-cost, scalable method for configuring public instruments and an empirical test of micro-level spatial cues as invitations to musicking. Implications for music education include practical guidance on using spatial design to create low-threshold opportunities for inclusive, informal participation in everyday life.