Unfortunately I'm not sure how a judge would ever justify that. Half of a book is still under copyright of the whole thing. Original music in the background of a movie is still copyrighted as part of the movie, even if a loud action scene is taking place on top of it. So even with a dial tone sound overlaid, that wouldn't change the fact that the music part of the recording has been published.
I don’t know if publishing 1/2 a book would protect the first half or not, but presumably the second half would have entered the public domain in your hypothetical example.
> Half of a book is still under copyright of the whole thing
But what was described isn't "half of a recording". Imagine the "publish to extend copyright" applied to books too - would publishing the book with half the text blacked out still extend the original book's copyright?
That's just my naive take on it (i know nothing about copyright law). Your movie music argument might already be enough to show that I'm incorrect.
What I meant was, the recording is half dial tone and half music, because they're overlaid with each other.
Subtract the dial tone and the music part is "half" the total copyrighted work (which includes the dial tone).
But the music part is still 100% copyrighted. Same way that if you publish a book with 200 pages, pages 1-100 are still 100% copyrighted even though they make up only half of it.
I would think you instead would have copyright on the new bit that is mixed in, and because of that, the combined version as a whole still contains your copyright and therefore cannot be copied freely.
I don't think that would give you any new rights over the original work though.
But perhaps crucially would give you effective financial control via online tools that look for a musical fingerprint?
If the public have the rights but can't exercise those unimpeded then the erstwhile rights holders get to retain the financial benefit and prevent full effective entry to the pubic domain.
I’ve heard stories of people uploading their old works to YouTube’s ContentID system so it will remove them from an old account they can’t access anymore.
It's easy enough to filter out specific frequencies - this should work to the extent that the dial tone track doesn't overlap in frequency with the rest of the sounds.
An interesting ruling might be only the dial-tone version had it’s copyright extended as the original had not been released.