Quote:
Not quite, Brid

. The first syllable in "leabhair" = 'lyoh' (big y-glide, 'oh' as in English 'more'), but no y-glide in "labhair" of course - like English 'lore'. Is é Lughaidh a chuirfeas miniú níos cruinne air.

níos cruinne? níl mé cinnte. Is maith a mhínigh tú féin é:
leabhair > lyoh-y (btw you wouldn't use that form because the genitive is "leabhaire" since it's feminine in Ulster, and the plural is normally leabharthaí)
labhair > loh-y
They sound a bit more similar when lenited, because the y-glide of "leabhair" then disappears, the l is still slender but it's not as evident as in the unlenited form. But you still hear the difference...
Actually the difference is the same in Connemara, the main difference between leabhair and labhair is the same as in Ulster (of course, in Connemara you have a diphthong for -abha-, and no y-sound at the end as we have in Gaoth Dobhair):
I guess "lyow-irh" and "low-irh" in Connemara then, same distinction with the first consonant

Concerning the other words:
súil /su:l'/
siúl /s'u:əl/
cathair /kahej/
ceathair /k'ehej/
(GD pronunciation, of course).
I noticed that in Northern Donegal, slender n's after back vowels tend to be double (ny-sound), maybe because the difference is clearer, from a single broad n. Sometimes it happens with L too.
I noticed that while listening to native speakers like Mairéad Ní Mhaonaigh (she pronounces "a' cheoil" as if it were "a' cheoill", and words that end with -áin as if they were with -áinn). Maybe older speakers like John Ghráinne wouldn't do that (I have to check

).
Also, and this happens with all Ulster speakers (native ones, I mean) I think, slender single n between vowels is pronounced as if it were double (ny-sound, again):
báine is pronounced as if it were "báinne" ie. bweh-nyeh" (the bweh- is long, of course), while C and M have "baw-neh" (slender single n).