Audio mastering — Duplicate key report + Explicit missing-value fill: Duplicate key report + Explicit missing-value fill for supplied audio mastering records (integrated_lufs, true_peak_db). Up to 200 rows; 2 independent reports using shared local analytical engines. No live lookup, prediction, professional assessment or external action. 0.01 USDC includes 2 supplied-data reports for up to 200 rows.