Quote Rob C.:
Just for clarification, Mr Trumpet's hope that MCPS/PRS notifications are "evidence of authorship" doesn't work out. Neither MCPS or PRS keep any record of the composition itself. The Library of Congress does (as part of USA copyright registration) but EU copyrights are respected by the USA through WIPO (AFAIK).
Hey! That's Mr Trumpet to you...oh, well anyway.
If you have a track with MCPS, that tends to imply that it's been released - not always, but you can't generally register with them unless it has been released officially. Hence you have a recording in the public domain, ergo proof of ownership.
They may allow some to be registered which aren't, but that will be the exception as the point of the MCPS is to pay you for royalties. Royalties on recordings in the public domain, which could be used as evidence if necessary.
I'm still waiting to hear of an example when any of this actually happened to a hapless unsigned individual posting demos to unscrupulous labels, mind.