An interesting collection of accents here.
The Chorus is sung by all six singers. Each singer has one stanza to sing alone.
This is a fairly modern song, put together some time after 1971. But all the words (except perhaps part of the chorus) were written in the middle of the 18th century, and the 20th century song came from putting together stanzas from two or more different poems by Seán (Clárach) Mac Domhnaill and some from songs which may have been written by him or may not, but are at least quarter of a millennium old. And the six stanzas here are not the whole song, there are quite a few more - but six stanzas and choruses is probably as long as modern audiences will accept, so most versions performed are shorter than this version.
The chorus sometimes has "chuaidh" and sometimes "luadh" in the last line - and in the final chorus, where the line is repeated, it has one of each. My hearing of Irish when six people with five diffeent accents are singing is not good enough to get which chorus has which word accurately, but I think the first five are all "chuaigh" and "luadh" comes in right at the end.

I suppose it's inevitable that someone will ask why I've named Iarla as the main artist and the others featured, so I had better explain. First, these six never had a name as a group - they did this one song together as part of the TV series "The Highland Sessions" which has now been made into a (DVD) album; and each of them did other bits in that series, as did 24 other singers, so that using the name of the series to identify just this group wouldn't work. And listing all six names as a single artist probably wouldn't work either. So I picked the one of the six who had, as a child, been present when the 20th century song was created and had been a member of the choir which first sung it. I suppose I could have picked Mary Ann (a Scot) as she was series presenter as well as one of the singers, or Allan as he too had a wider role in the series, but I didn't.