Melody from Rossini's Opera - Public domain version?

[Amelia.pd]

The melody to the song "Green Hills of Tyrol" was composed by Rossini and taken from the opera William Tell. In 1854 a Pipe Major named John Macleod arranged this melody for his Pipe Band during the Crimean War from 1853-1856. Assuming that John Macleod died before 1955, wouldn't this melody be Public Domain if it's used without its copyrighted lyrics which led to it being called "A Scottish Soldier"?

Please respond if you have any thoughts at all on the copyright status of "Green Hills of Tyrol" - It would be much appreciated

[Melodia]

Certainly the melody would be PD even if the lyrics aren't. A well known case of this is Happy Birthday.