The Song of Durin
, performed by the Tolkien Ensemble. Poem appears in FotR, Chapter 4, A Journey in the Dark.
Gimli sings this in Moria, the night before they find Balin's tomb. (It's fair to say that Thorin and Co. would have also known this song, however.)
Tolkien describes it as a chant. The Tolkien Ensemble performs it more like a hymn--though the treatment of each stanza varies nicely.
I did particularly like how they've done the last stanza (the world is grey, the mountains cold
...)--would totally love to hear RA sing that deep bass acapella...with the last two lines sung by the company.
And of course, in FotR, Sam particularly liked the line "in Moria, in Khazad Dum."
Thanks for sharing, Na Vedui! Very cool.