dublin writes: Mark Steyn's first-year anniversary "Song of the Week" column details how a single note keeps ASCAP's #1 song from the public domain — making it one of the shakiest, yet most feared, copyrights imaginable. An excerpt [brackets mine]: Warner Chappell's grip on "Happy Birthday To You"
...rests on the curious proposition that there are two entirely different songs: [one public domain, the other enforcibly copyrighted, 42 years apart] ...the only musical difference between the two songs is one note... In no other circumstances has that ever been regarded as sufficient to make something an entirely separate composition".
Why is this copyright still so strong, especially with such clear evidence of widespread use for decades before the copyright date?