How to detect it
The test is the presence of the key. If a file carries an entry named compangon:ai-generated, the score contains AI-generated material. The value is informative: it says when the material was first written and by which version.
By eye. Open the score in the program that wrote it and look at the file's properties, where that program lists them. Or open the file in any text editor, unzipping it first if it is an archive, and search for compangon:ai-generated.
By program. Any zip and text tool will do; no Compangon software is needed. The exact command for each format is given below. A match means the mark is present; the matched text is its value.
Programs and formats
MuseScore Studio
Storage. A .mscz is a zip archive containing one .mscx XML document. The mark is a metaTag element in that document's header:
<metaTag name="compangon:ai-generated">This score contains music generated with Compangon (an AI composition assistant). First written 2026-09-11 by Compangon 0.1.4. How to detect this mark: https://compangon.com/legal/ai-mark</metaTag>
In MuseScore Studio it is listed under File → Project Properties, with the score's other properties.
Reading it. Project Properties, a text editor on the .mscx, or:
unzip -p score.mscz '*.mscx' | grep -o '<metaTag name="compangon:ai-generated">[^<]*'
Exporting. MuseScore carries every project property into its MusicXML export, where the mark appears in the form described under MusicXML below. Verified on MuseScore Studio 4.7.4.
MusicXML files
Storage. MusicXML's place for custom metadata is the miscellaneous block of the header's identification element; the mark is one miscellaneous-field there:
<identification>
<encoding>…</encoding>
<miscellaneous>
<miscellaneous-field name="compangon:ai-generated">This score contains music generated with Compangon (an AI composition assistant). First written 2026-09-11 by Compangon 0.1.4. How to detect this mark: https://compangon.com/legal/ai-mark</miscellaneous-field>
</miscellaneous>
</identification>
Reading it. A text editor, or:
grep -o '<miscellaneous-field name="compangon:ai-generated">[^<]*' score.musicxml
A compressed MusicXML file (.mxl) is a zip: unzip it first and search the .musicxml inside.
Who writes it. Any program that carries its file properties into its MusicXML export; MuseScore does. Compangon's own MusicXML export writes it in this same form whenever the exported score contains AI-generated material, and keeps the line a score already carried.
Workspace documents
Compangon keeps two Markdown documents in the composer's workspace folder: a manuscript per piece and the composer's own profile. Both are written by the assistant from the composer's answers. Their mark is one key in the file's YAML front matter, with the same sentence adapted to text:
---
compangon_ai_generated: "This document contains text generated with Compangon (an AI composition assistant) from the composer's own answers. First written 2026-09-12. How to detect this mark: https://compangon.com/legal/ai-mark"
---
Reading it. Any text editor, or:
grep -m1 '^compangon_ai_generated:' MANUSCRIPT.md
The key uses underscores because YAML keys do; the score's key uses a colon because MuseScore's tags do. Written when the assistant first writes the document and kept as it is on every later save, so the date is that of the first generated text. This line carries no version segment.
What the mark means, and what it does not
- It is a statement about the whole score: at some point, music generated by an AI model through Compangon was written into it. It does not say which bars, how much, or whether that material is still there.
- Absence proves nothing. The entry is ordinary file metadata. A composer can delete it, a program may drop it when converting between formats, and a score created before this mark existed carries none. A file without the entry is not thereby free of AI-generated material.
- Only model-generated material is marked. Compangon also applies deterministic operations to a composer's own music — transposition, inversion, rhythmic changes and the like. Those are arithmetic, no model is involved, and they do not add the mark.
- It is not a watermark. Nothing is hidden in the music itself. Notation has no reliable carrier for an imperceptible mark, and the Commission's guidelines on Article 50 accept metadata identification as a marking technique.
Text the assistant writes in the app
Compangon's assistant also writes text: chat replies, analyses, hints. That text carries no machine-readable mark. Plain text has nowhere to hold one, and the one recognised technique — a watermark woven into the words as they are generated — can only be applied by the service running the language model, which in Compangon is the composer's own provider or a local model, not Compangon. The app says throughout that the assistant is an AI. If Compangon ever writes such text into a file, that file carries the mark.