The Loud Music Of The Sky Summoning

What I am, I must not show
What I am thou could (not know)
Something between heaven and hell
Something that neither stood nor fell
Something that through thy wit or will
May work thee good, may work thee ill
Neither substance quite, nor shadow
Haunting lonely moor and meadow
Dancing by the haunted spring
Riding on the whirlwinds wing
Far less happy, for we have
Help nor hope beyond the grave
Man awakes to joy or sorrow