Maps, dictionaries, and similar sometimes contain copyright traps, which are intentionally false information like a street that does not exist. The point of these is that when somebody plagiarises the work and includes the copyright trap, this evidences the plagiarism.

Is it known that such copyright traps exist in musical scores as well?

I am asking because I sometimes notice notational quirks in arrangements of public-domain music, such as:

  • A G♯ when the rest of the score uses A♭ in analogous places (and it’s a piano score such that the distinction between G♯ and A♭ doesn’t matter).
  • Different fingerings for analogous sections.
  • Dynamic indications that only affect breaks.

These are without any real effect, but so bizarre that they are unlikely to be just mistakes. My best explanation is that they are copyright traps. And since these are arrangements, a copyright trap actually has some purpose: For example, without one, it might be difficult to prove that somebody plagiarised your arrangement of Pachelbel’s canon instead of copying the (public-domain) original.

Mind that I am not asking about the legal implications of these traps or whether they are a good thing, just whether they exist.

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    I've heard anecdotal talk about the opposite, that International music editions (notoriously iffy) would copy older editions but intentionally introduce errors so they could claim to be distinct Jan 11 at 19:04
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    I don't remember what piece it was, but in one particular score that I read, I saw several minor sevenths where there should have been harmonic sevenths.
    – user59346
    Jan 11 at 21:07
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    "and it’s a piano score such that the distinction between G♯ and A♭ doesn’t matter": this isn't correct. The distinction between G♯ and A♭ almost always matters in piano music, just as it almost always matters in any staff notation. What is "Dynamic indications that only affect breaks"?
    – phoog
    Jan 12 at 0:06
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    The distinction between G♯ and A♭ almost always matters in piano music – How would it matter? I am pressing the same key. I can only imagine some fringe cases, where I tune the piano for this particular piece. — What is "Dynamic indications that only affect breaks"? – Something like forte, break, piano as opposed to forte, some notes, piano. You are essentially instructed to play a break (and only that) with higher volume.
    – Wrzlprmft
    Jan 12 at 6:45
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    "How would it matter?" First, it's difficult to read enharmonically misspelled music. Second, the reader has to decide whether you're trying to convey something specific and meaningful, or you don't know what you're doing. The choice of G sharp or A flat is dictated by the musical function or role of the note; the fact that this may also have implications for tuning is secondary. Can you add some examples of these "quirks"? They may be easy to explain as legitimate choices, but without seeing them we can only speculate.
    – phoog
    Jan 12 at 10:21

1 Answer 1


The comparison with maps doesn't really hold:

With notated music, the typical piracy threats are:

  1. Stealing from a composer by notating and distributing their composition without their permission. Easy to prove or disprove the piracy with the composer: Either you got permission or you didn't.

  2. Stealing from a publisher by copying their sheet music (even if the copyright of the composition itself is already expired). This could be by scanning printed sheet music or copying the PDFs. Even if you do the effort of masking out the copyright statements of the publisher, there's so many variables in music typesetting (spacing, fonts, stem directions, ...) that it should be obvious to prove the piracy.

With maps, there is no composer; nobody has copyright on the earth. And anyone that creates a map is bound to come up with very similar results. Furthermore, you can easily reformat stolen map data to make it look like your own. This is harder to do for music. I suppose you could process sheet music by optical music recognition software, reformat and republish the results... But I doubt that this constitutes a big loss for music publishing companies (and, if the copyright of the composition hasn't expired, then you can still get caught for type 1 piracy).

  • And anyone that creates a map is bound to come up with very similar results. – Well, that’s more or less my point: Every simple arrangement of, say, Pachelbel’s canon will be similar. Maybe less similar than maps, but similar enough that it’s difficult to claim that somebody copied from the arrangement instead of the original. — you can easily reformat stolen map data to make it look like your own. This is harder to do for music. – Map data maybe, but not compiled maps. I would argue that scores can be easily copied once you know how to typeset scores.
    – Wrzlprmft
    Jan 11 at 20:21
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    @Wrzlprmft if two people make arrangements of Pachelbel's Canon, they aren't the same except by chance or by copying. The point of putting a copyright trap in your map is to identify people who got their facts from your work. In an arrangement of Pachelbel's Canon, the only facts are the original work itself, which doesn't change over time as geography does, and where using a recent edition isn't going to save anyone much time compared to using an old one. Any notes in your arrangement that differ from the original aren't a copyright trap; they're the arrangement itself.
    – phoog
    Jan 11 at 23:52
  • Another way of looking at it, since you mention fingering in the question: if Theodore publishes an edition of Pachelbel's Canon with fingerings, there's no point in varying the fingerings in analogous places because all of the fingerings are protected by copyright. If the fingerings in Carl's edition match, they match, regardless of any internal inconsistencies in the source.
    – phoog
    Jan 12 at 0:21
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    @phoog: To take up the fingering example, of course all the fingerings are protected by copyright, but Carl may claim that his fingering matches Theodore’s not due to plagiarism but because it is one of few reasonable fingerings for the piece. If however Theodore is using some unusual fingering where the normal reader wouldn’t notice (e.g., because it’s a repetition), and Carl copies that, Carl’s claim would be disproven. Finally mind that my question is not about what is technically copyright infringement or what is litigable, but whether any publisher chose this as a precaution.
    – Wrzlprmft
    Jan 12 at 7:29
  • @Wrzlprmft fair points. At first I was thinking only of musical arrangements, where these considerations aren't really applicable. But for other editorial elements there's more of a case to be made.
    – phoog
    Jan 12 at 10:46

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