I’ve always regarded these as two separate tunes although they’re obviously similar
the first parts are definitely not the same and ‘the humours’ has a third part, although you can’t not notice the similarities in the second parts
the differences are too big for me to see them as the same tune
what’s the consensus view out there?
Related tunes or versions of each other.
To me, the differences are within the range of variations I might play anyway when performing either tune. Which means they’re the same tune in my repertoire.
You would add a whole third part to a tune as a normal variation?
The A parts are different enough that you can’t play them together, and if you were doing that level of variation as anything other than a performance / show-off, I’d think you were just screwing up the tune… (I mean, if someone else had started the other version).
In other words, I’d never classify them as a blanket “same tune”. It would always be “they’re versions of the same tune” or more likely “they’re related tunes or variants”.
to me the differences in the first part are subtle but quite pronounced as well so I don’t think i’d see them as interchangeable
reminds me a bit of the relationship between the frieze britches and I buried my wife - very close cousins but not the same tune I think
the way that the first part of the humours of ennistymon is played also reminds me a bit of the first part of the queen of the rushes except played in g not d
Moi? Since we’ve never played together, Nico, and your spies at my sessions can kindly hold their tongues … I think I can safely say that, no, I never screw up a tune. Never, ever. Yeah, that’s it … 
Seriously, using TheSession as a reference, do you consider the first setting there as Humours, and the second setting as Coppers and Brass? Yes, those A parts are incompatible.
Not as a melodic variation, no. But choosing at times to play a different subsets of a multipart tune - sure, why not.
I always considered them just distant versions of each other. a bit like Colliers Reel and My Love is in America. They probably were the same tune 150 years ago.
Tommy
The Fiddler’s Companion has some interesting notes on both titles:
http://www.ibiblio.org/fiddlers/COO_CORI.htm#COPPERS_AND_BRASS_[2]
http://www.ibiblio.org/fiddlers/HUMOURS_HUMP.htm#HUMORS_OF_ENNISTYMON_[1]
The book, Learn to Play the Uilleann Pipes from the Armagh Piper’s club gives a somewhat simplified notation of Johnny Doran’s playing of ‘Copper and Brass’ with three parts. . .
Bob
Oops, just check my copy of the book. The credit goes to Felix. . .but I’m guessing he got his setting from Johnny. . . .
Bob
The book, Learn to Play the Uilleann Pipes from the Armagh Piper’s club gives a somewhat simplified notation of Johnny Doran’s playing of ‘Copper and Brass’ with three parts. . .
They actually give a two part version with the repeats written in full, with the variations that were played.
I think it’s pretty apparent that they are different, but related tunes. You can’t play the two A parts together without it sounding like a train wreck and the Humours of Ennistymon has a third part.
I have a recording of Johnny Doran playing Coppers and Brass with two parts.
Bought my copy in 1975; it’s still one of my favourite collections of tunes.
@MTGuru - I didn’t mean to imply you specifically, but rather a general “you”. And it’s of course context dependent (which I fear was not clear) - if someone starts Coppers and Brass, and other people jump into Humours, the others are screwing up the tune (and not listening well).
I get your point about the “subsets”. It’s a bit like languages - there might have been some “parent” or “proto-tune” that these two tunes came from, so one could possibly think of the whole group as “one tune”, but I prefer “one tune family”.
Referring to http://thesession.org/tunes/228, yes, the first two settings are distinct tunes, albeit tunes which are related, are variants of each other, or are different versions (I would, at this stage in my learning, go with the second definition).
All understood, Nico. Thanks! 
Just noticed a similar similarity between ‘the beauty spot’ and ‘sporting nell’. The second parts are different enough but the first are perhaps interchangeable. I think I’ve heard mick O’Brien play both and only recently discovered they were not the same tune.