Yes, that Tam Lin site is nice, if a bit fannish. (I actually supplied her with about half of the discographic references some ten years ago, hence she writes: "My thanks to Steve Winick for supplying the url as well as much information below."

The site Tim put you on to is a bit more comprehensive, and lits the Duncan Williamson recording (which probably counts as a "source singer recording," although I understand Duncan adapted it from his grandmother's version with much recourse to books--so it will depend on what you want to consider a "source singer.")

Also listed on Tim's site are two Eddie Butcher recordings. I'd caution that the second of those is a version of "The Stolen Bride," a ballad that exists in Irish and English. Though it's similar to Tam Lin, it's obviously different in many particulars, especially that the person abducted is a young wife and it is her husband who must rescue her. (Very different from a knight being abducted and rescued by a girl he meets AFTER being kidnapped.) You can find modern revival recordings of this song from the group Cran (in English) and from Padraigin Ni Uallachain (in Irish). I don't know if the first is indeed Tam Lin, but I suspect so, as the line about Halloween doesn't occur in Stolen Bride versions that I know of.

As for The Muckle Sangs, this CD had a huge booklet that sold separately, and I didn't get it. So there's limited info in the booklet I have, and I don't have time to listen and report back now! But it lists two versions, one by Johnston and the other by Willie Whyte, and together they are seven minutes long--so there's probably a good chunk of the story there, but not as much as in Mike's (which was originally Bert Lloyd's adaptation).