So I am designing a mobile app that transposes music for the user. The user can only transpose four notes at a time, and they are required to input the notes themselves. Are there any copyright laws of any kind that might cause problems with my app?

  • Limiting to four notes at a time will not stop someone from using your app to (possibly) violate someone's copyright. All it will do is make your app annoying to use.
    – Brandin
    Commented Jul 23, 2019 at 13:38

1 Answer 1


Four notes seems an odd limit, and I wonder if this would be useful to anyone. But that is not the question. If a user types in a copyrighted composition note by note and transposes it, the user may well have infringed the copyright by creating a derivative work. But the app designer and proprietor will not have infringed, unless it was advertised with such a use in mind, knowing that infringing uses were likely.

  • It seems to me that the developer of an app like this is as liable for copyright violation in the described situation as would be the developer of a word processing program if someone used it to type out a copyright-protected article or book. A transposition of a musical work is not sufficiently different to enjoy its own protection as a derivative work, so the application isn't appreciably different from a word processor.
    – phoog
    Commented Jul 20, 2019 at 20:13
  • @phoog But this is a far more specialized app. It's like a word processor whose only function is to change case. That can be used to create a modified version of a text, but is poorly adapted to creating an original text. If marketed for creating a modified version, under circs where the seller should know it will be used for infringement the seller might be liable. And a mere transposition might not be original enough for a separate copyright, but it is still derivative and an infringement if done without permission. Commented Jul 22, 2019 at 22:30
  • One of my points is that I don't think a transposition is a derivative work: it's the same work. To use the case analogy, if you write out a famous novel in all caps you haven't created a new novel derived from the original; you've created a copy of the same novel.
    – phoog
    Commented Jul 22, 2019 at 22:51
  • @phoag. Perhaps. But whether you call it a derivative work or a copy it is still an infringement unless done with permission, or unless fair use applies. An app predominately used to engage in infringement, advertised with a view to infringement, when the seller knew or should have known infringements were likely, may well subject to seller to liability for contributory infringement. This is true whether the infringement consists of making copies or creating derivative works. Commented Jul 22, 2019 at 23:00
  • Sure, but four notes sounds like fair use to me. And regardless, there's lots of public domain music out there.
    – phoog
    Commented Jul 22, 2019 at 23:38

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