Heill Dan!

> So, 'allr' would normally be used in the plural in this context? I suppose I was
> fooled because 'all', being a collective noun, is always in the singular in English.
> How would you distinguish singular and plural uses of a word like 'allr'?

For example:

Allr sá dagr = All that day
Allir þeir dagar = All those days

> I'm even more curious now. If it's not bilabial or a labiodental fricative, how is
> it articulated?

Hmm... It is articulated by touching (but not holding) the upper teeth to the lower lip.
I think that makes it a labiodental approximant.

Kveðja,
Haukur

--
Svá æ folkmýgi.