[Raynor]

And we don't know what she sang.

From the Lay of Leithian, HoME III:

Then did she lave her head and sing
a theme of sleep and slumbering,
profound and fathomless and dark
as Luthien's shadowy hair was dark
each thread was more slender and more fine
...
His dreadful counsel then they took,
and their own gracious forms forsook;
in werewolf fell and batlike wing
prepared to robe them, shuddering.
With elvish magic Luthien wrought,
lest raiment foul with evil fraught
to dreadful madness drive their hearts;
and there she wrought with elvish arts
a strong defence, a binding power,
singing until the midnight hour.
...
With arms upraised and drooping head
then softly she began to sing
a theme of sleep and slumbering,
wandering, woven with deeper spell
than songs wherewith in ancient dell
Melian did once the twilight fill,
profound, and fathomless, and still.
The fires of Angband flared and died
...
Suddenly her song began anew;
and soft came dropping like a dew
down from on high in that domed hall
her voice bewildering, magical,
and grew to silver-murmuring streams
pale falling in dark pools in dreams.

These quotes are proof of the magic in her words - she is the chief enchatress among the elves; but there is more to her merit, since magic itself couldn't move Mandos, only art (or Art maybe) from Of Beren and Luthien, Silmarillion:

The song of Luthien before Mandos was the song most fair that ever in words was woven, and the song most sorrowful that ever the world shall ever hear. Unchanged, imperishable, it is sung still in Valinor beyond the hearing of the world, and the listening the Valar grieved. For Luthien wove two themes of words, of the sorrow of the Eldar and the grief of Men, of the Two Kindreds that were made by Iluvatar to dwell in Arda, the Kingdom of Earth amid the innumerable stars. And as she knelt before him her tears fell upon his feet like rain upon stones; and Mandos was moved to pity, who never before was so moved, nor has been since.

I just see her as a slightly less trashy Paris Hilton....

I doubt this was Tolkien's impression of his wife

Originally Posted by Letter #340

I have at last got busy about Mummy's grave. The inscription I should like is:
EDITH MARY TOLKIEN
1889-1971
Luthien
brief and jejune, except for Luthien, which says for me more than a multitude of words: for she was (and knew she was) my Luthien.