Ancillary body movements in piano performance: a critical narrative review of structural coupling, audience cues, and cognitive-scaffolding claims.

Although piano performance is often treated as centered on sound production, it also involves body movements commonly discussed as ancillary, whose observable role extends beyond immediate sound production. These movements have often been discussed through broad embodied-cognition frameworks, yet the empirical basis for specific mechanistic claims remains uneven. This critical narrative review synthesizes research on movements commonly discussed as ancillary from two related but unevenly developed bodies of evidence: their reported relationships with musical organization in performers, and their role as visual cues in audience evaluation. On the performer side, kinematic findings suggest that movements commonly discussed as ancillary are often systematically related to phrasing, meter, and expressive organization, but direct evidence for cognitive-load reduction remains limited. On the audience side, audiovisual studies indicate that visible kinematics can substantially shape judgments of expressivity, emotion, and performance quality, although the strength of these effects varies across tasks and study designs. Across both domains, the literature remains constrained by small samples, limited ecological breadth, and an overreliance on correlational evidence. We therefore argue that current findings support the relevance of movements commonly discussed as ancillary as structural and perceptual cues, but do not yet justify strong claims that they function as cognitive scaffolds. Future work should combine controlled kinematic manipulation with multimodal measurement to clarify how these movements may simultaneously serve overlapping communicative, regulatory, and biomechanical functions.