I just read the article. It is talking about the master right not falling into the public domain, not the song:
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The change applies to the copyright on studio recordings, which is often owned by record labels, rather than the right to the composition, which is owned by the songwriters.
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Musicians may have written the songs but they almost never own the master rights unless they produced their own recordings, which they didn't if they were on any sort of label. This won't help musicians, it will help record labels. The article talks about this.
There was a pretty interesting article in the new york times recently about master rights possibly being reclaimed by musicians even though they did not produce the recordings themselves.