I'm reviewing this story because you requested a review. All the thoughts expressed here are given for the purpose of helping you evolve into an even better writer than you already are.
The story is actually really good, but there are a lot of areas that need some editing. If I am not mistaken it was written for Sinister Stories back in October. If so, it was a unique approach to the piano prompt.
The title is great and matches the story. If one likes a good horror story, it would heighten curiosity for the darkness that lurks inside.
That first line hints to something Sinister and dark, which is a good start. The issue is that you begin with improper punctuation. Below is the introduction with the correct punctuation.
This story is a warning to all who will listen. I don't have long until "She" comes, so here goes my story.
By the way the red lettering works well here. It causes the word to scream off the page, hinting that "she" is dangerous. Though, I would suggest bold lettering, rather than quotation marks. It would have the same effect, while not distracting from the actual dialogue.
There is very little dialogue. The dialogue that is there works. Her words are quite terrifying. Though, there are some punctuation issues in her speech and it is too wordy. Also, towards the end of her words it gets confusing. I think she is trying to express that you have woken something that is worse than any pain the Devil could inflict and that she is going to harm everyone you love?
There is an area where you express internal dialogue. Italics work better when expressing unspoken words.
This is told in first person, as if you are trying to write this down in a hurry, before She returns. We get a lot of background story, and I can see what you were trying to do. In my early writing, I used to do exactly the same thing.
It seems that you are trying to give a clear image of the writer, but a lot of the details are errellivent. What does working at the music store have to do with the plot? Unless there is an eery attraction to the piano or something equally suspicious about the music store, it is unimportant to the story. But, the piano is arriving at the home, making the whole music store unimportant.
Simply letting us know that he arrived home from work and the piano was there is enough.
The descriptions of She are done particularly well. You added sight and smell, which help show Her to your reader. I imagined, through your words, a rotting female, visually and in smell.
We have a haunted piano that releases an intity who is going to destroy everyone you know. That is a great plot for a horror story, but there are some holes in the showing of the story.
First, we are told that you are receiving a new piano. If the piano is haunted, wouldn't it be antique? Secondly, you are trying to write this before She returns, but I am confused to where she went.
At some point you mention some writing on the piano. If you mentioned that the writing looked hieroglyphic or ancient, it would hint at something scary about the piano.
When you describe what the piano actually looks like, I would suggest showing the character's attraction to it a little. For example, you could touch it and it feels worm as if alive, or maybe electricity runs through your fingers while you touch the mahogany finish.
Improper comma and punctuation, or lack thereof is a constant issue throughout. Most of it would be caught if you wrote your story in Microsoft Word or a cheaper equivalent.
It is apparent that you have a wonderful imagination and this story has the capability of being really good. You just need to hone in on your skills a bit. My thoughts expressed in this review are meant to help you do that.
Thank you for sharing your writing. Remember, this is the opinion of one person. It is up to you, the writer, to decide which advice to apply. Hopefully my thoughts on your writing have been helpful.