Madame Shadow plays across the way
Each key is hers to favour as she may
Tonight I hear her pleasure in the dark
As her silhouette by candle flickers

Her beauty stands unmuted by the shade
And I ponder how her hands are made
All soft and white to draw such melody
How each inch of ivory must dream
Of the next note it shall call at her beckoning

Her back a gentle curve
A poise to her wrist
As she raises her glass of unknown potency
Poisons her perfection, and let's me in

I call away, drift and waver
Search my voice to find means of her favour
Downtrodden slip from pleasure into pain
And cease, her caress, quite suddenly

Madame Shadow drips tears on ebony
To hear my soul as such poured out of me
Such radical displacement of emotion
Such hurt
We raise our glasses to one another and stand
Our neighboured souls know pain
Tomorrow Mister and Misses Shade
Shall marry in the rain
That is amazing...
That song is...i cant even explain

That lady that inspired it must be perfection
Grammar: third stanza, it's "lets"

The structure isn't constant- Having it more regular would help with the flow of the piece.

Some of the word usage seems a bit excessive, a bit overdone. At points it seems as if you didn't really have a meaning to the words but they just sounded cool so you put them in, but that's just the impression I got.

I like the ending, the Mr and Mrs Shade bit.
Overall not bad, maybe a bit more variety would do it good.