- count usages don't take the indefinite article
is not considered binding by many. CGEL uses the test
- can a numeral or equivalent ('a dozen ...') be inserted in such a string?
as the deciding factor.
Here, 'The drink had put him in an amiable mood' cannot be rendered say 'The drink had put them in six amiable moods' and so the usage is deemed 'noncount'. See EA's answer at a blinding light / blinding sunlight / a blinding sunlight for further discussion.
A count usage of 'mood' is 'I basically have two moods – either let's do something spontaneous and awesome, or let's just lay in bed all day and forget the world exists.'
Inclusion of a definite article with a non-count usage can certainly make a difference to what is being communicated. In the question referred to, an article at Useful English contains:
In formal writing and literary works the article a/an may be used with
some uncountable abstract nouns to show an unusual or temporary aspect
of something. The indefinite article here has similar meaning to:
such, certain, special, peculiar....
- Formal / literary style: The director spoke at the meeting today with an enormous enthusiasm.
- Standard / everyday style: The director spoke at the meeting today with great enthusiasm.
However, certain fixed expressions involving non-count usages invariably include the indefinite article. There is no 'standard/everyday' alternative, so the acceptable version perhaps loses impact.
The noun involved does not usually take the plural form.
Many use prepositions peripherally (metaphorically):
- The room was in a mess.
- The rooms were in a mess.
- It must be said that he does have a temper.
- She was in a frenzy.
- He was in a foul mood.
- They were in a foul mood.
- The drink had put him in an amiable mood.
- They went to work with a vengeance.
The example obviously referring to a more general, 'homogenised' referent
- Style allows writers to create mood and evoke feeling in readers.
is obviously better without the indefinite article, especially in a literary commentary as here, though 'a suitable mood' would work if it didn't not pair too well with 'feeling'. Indeed, 'a mood' without modifiers is probably often taken to be equivalent to 'a bad mood': 'My, we are in a mood today.'