I must confess that it's a new one on me, so thanks for bringing it up Ian.
From a songwriting point of view I think it's often fascinating to hear the writer's version of things that become established classics, even if they don't finish up as being as good a record for whatever reason as the more established 'hit' version.
Interesting that Copanni's line about 'on a cloud to Napoli' is not in the Jackson Sisters reading of the song. Yes, he's not the world's greatest singer but this is still a very nice pop-soul record, understandably more about the song than the Jackson Sisters version, which you'd have to say is more about the production and arrangement.
Let's hope he's done OK in royalties over the years from it.