In general, the disclaimer/guidance on the style guide is sufficient, and there is no need for us to contact the copyright holder directly. It really is for the end-user of the score/scale in the app to comply with licensing arrangements. I would tend to err towards ‘publish, and seek forgiveness’, if someone asserts a breach of licence.
Occasionally we do come across situations where a copyright holder asserts a right to check that implementations are representing the score faithfully, and we do try to clarify our status, given we are not really an implementer. These can sometimes be quite difficult discussions as the agencies involved tend to see us an a typical app developer with a ‘product’ but these are comparatively rare situations.
@heather.leslie and @siljelb will have mor experience of recent discussions.