ACTA Brief 04 — Four Layers Between a Song and Its Proof: Detection, Declaration, Verification After the Fact and Evidence During Creation. A Map of Music Provenance by What Each Layer Can Establish

"Provenance" now names four different jobs in recorded music. Detection examines a finished file and estimates whether a generator produced it. Declaration asks the party delivering a work to state what is in it. Verification after the fact examines a finished master later and issues a verdict on whether a person can credibly demonstrate authorship of it. Evidence during creation records the making of the work while it happens, where it happens. Each layer observes the work at a different moment and can answer only the question that belongs to that moment. This brief proposes a classification of the field by two criteria, the moment of observation and the object examined, and uses it to map the instruments and organisations active in 2026, with dated public sources. It finds that the first three layers are commercially or institutionally established, that the fourth has several independent occupants but no standard way to be received, and that recent rules (KOMCA, August 2026; ARIA, August 2026; IFPI chart principles, July 2026) ask questions that only the fourth layer can answer while specifying only the formats of the second. The brief makes no claim about the authorship of any work and no claim that any layer replaces another. It argues that the layers are complements, and that the missing piece is not another layer but the interface through which a declaration can rest on a record.