Filk. Eh, I'll try and define it, because there is a lot of Tolkien filk out there. Most of it is humorous/ satire, which isn't quite my cup of tea. But there are a few...
Filk is sometimes described as a cross between "folk" and "Filch" (as in, I filched someone else's tune and wrote my own lyrics to it.) in that sense, one can easily see it's a time-honored tradition. But it has become a subculture. There are conventions, etc.
I'm not sure why Leslie Fish falls into the Filk category; from what I've seen, her tunes are original, her lyrics profound.
You can find an mp3 of Julie Ecklar performing Leslie's "Fellowship Going South"
here. Have a hankie nearby.
Off Topic Edit: and if you are a fan of space shuttles and space travel, don't miss Witnesses' Waltz, listed below, also by Leslie.
[ 10:36 AM November 26, 2003: Message edited by: mark12_30 ]