think about famous (or not so famous...) songs that you know. then try to figure out if it would fit in the events of LotR or some other Tolkiens story.
(it would be nice, if you could find a link where to hear that song)
for example:
in Helm's deep Legolas doubts their changes to survive over the night. Aragorn starts to sing Madonna's 'Die Another Day'
( listen here - windows media )
i hope you guys understood my confusing explanation, so happy posting!