How do we or should we define the term "work"?

[yvanzo]

@Samsom_Productions

But however, at Music Brainz there also seems to be a confusion about the meaning of the term “work”.

I think you misinterpreted the first sentence of @CallerNo6’s answer about this.

@CallerNo6

I don’t think that’s quite correct.

See also the definition of Work entity in MusicBrainz documentation.

@Samsom_Productions

When I look at my own “works”, there pops up “Have yourself a merry little Christmas” […] That is not right, we are performers of that work not composers!

I disagree, this list of works represents your (recorded) repertoire. Moreover, it clearly distinguishes between writers (lyricists/composers) and other artists (performers), see the column “Writers”.