Music amplitude modulation and postural sway across visual contexts: A repeated-measures secondary analysis of nonlinear dynamics and model adequacy

Music amplitude modulation may alter standing balance, but inference depends on correctly representing the repeated-measures design and controlling analytic flexibility. We performed a source-faithful, bias-controlled reanalysis of 334 usable 60-second trials from 28 participants completing three visual contexts and four Mozart conditions. The sole confirmatory endpoint was log anterior–posterior root-mean-square center-of-pressure displacement, tested with 99,999 participant-blocked restricted permutations. Music condition affected displacement (F(3,301)=5.52, p=0.00003). The 0.1-Hz amplitude-modulated/no-music ratio was 1.129 (95% confidence interval 1.038–1.230). The visual-by-music interaction was unsupported. Multiplicity-controlled nonlinear and post-result spectral families were null. A delayed-feedback surrogate failed predictive and recovery criteria, and participant-held-out classifiers did not exceed chance. This is a robustness reanalysis, not an independent discovery.