Lúthien sings to Elbereth.
Likely written in the 1950s, the poem shares the same style with A Elbereth Gilthoniel. Unfortunately, there are some uncertainties surrounding it, since Tolkien did not provide a translation. And it should be noted that the syntax appears to be bent for the sake of the metre. However, most of the words used in it are attested elsewhere, and thus we have a relatively good understanding of what is said in it. One interpretation could be:
When the Moon, jewel of the firmament,
shines on the watch for us, Children of the One,
then flower and tree, listen in silence!
O Lady of the West, Starkindler,
to thee I sing, I Nightingale!