I'd like this to work, and kudos to the creators for having an interesting idea in a problem area. I've been surprised that copyright plaintiffs have been winning these cases, e.g. Marvin Gaye vs Robin Thicke, the Katy Perry case. Maybe this "all-melodies-ever" idea has an off chance to defeat copyright claims based solely upon melody, although I'm doubtful (that said, I haven't thought deeply about it and copyright law is filled with nuance).

But practically, most of these claims are not based solely on melody. For instance, a plaintiff beat Katy Perry based on expert testimony that the songs were similar "with regard to their pitch, rhythm, texture, pattern of repetition, melodic shape, and timbre."[1] The way these cases are being decided, plaintiffs could avoid dismissal by claiming copyright in some nebulous combination of protectable elements, even if melody is a key part of similarity.

One ray of hope: The Ninth Circuit Court of Appeals (which decides most of these cases, since it encompasses LA) is reconsidering these issues in the case where Led Zeppelin was accused of ripping off the Stairway to Heaven riff. The lawyers made their arguments last year, and we are waiting for a decision. A good decision could clean up the law governing these claims.

[1] http://www.fordhamiplj.org/2019/09/27/katy-perry-lost-her-da...