I like it; it's very poetic. The only thing is that you sometimes get so focused on the description of the piano that the words end up taking away from the image you're trying to create. You have to remember that you're elaborating on an EXTRACURRICULAR activity, so you need to emphasize that you play the piano regularly now. Also, you have to explain why this activity means so much to you. Does it help you remember your mother (My impression from the essay was that she passed away)? Was it a way of dealing with your grief or stress?
A few things:
It lay untouched for two years after my mother's heart attack, forgotten by world . (Try ending the sentence with "forgotten".)
I hauled the dilapidated red satin-covered (All the describing words are not necessary; maybe just leave it "the dilapidated piano bench") piano bench, emitting a groan of protest from the added weight. (After the imagery of the first few sentences, it's hard to picture this sentence. Where are you hauling the bench? Hauling is dragging, not carrying, so if you are groaning with the added weight of the bench, you need to change the word.)
On the music stand above (Above what?) , scattered composition sheets of Bach, Chopin, Beethoven, and the ever brilliant (You don't need this) Pandolfi, now yellow with age , were spread out, waiting to be read.
Their jet- black notes resembled minute insectspirouetting across the worn pages (Insects don't really pirouette; I'd just keep the last part of the sentence.) and scurrying to the double-barred ending.
As I ran my fingers over the keys lightly , a coating of dust began to become ingrained itself into my fingertips .
The plated ivory of the keys was hewed from the higher register, leaving the wooden stubs naked under the harsh glare of the lamp. (I had trouble understanding this sentence. Is "higher register" referring to pitch? How could something be hewed from it?)
The entire piano itself was of a dark arboreal shade, with the grain showing prominently in the foreground. (I would use a different phrase from "dark arboreal shade"; a lot of pianos are made of wood. Is it mahogany, maple, oak, etc.?)
The piercing resonance of strings rang through the course of my bones. The tune (Is it a song or just that one chord?) washed over me, soothing my soul. The bitter notes (What bitter notes?) were made honeyed again, concealed by the discordance of sound. (If they were made sweet again, how are they still hidden by disharmonious notes?)
Good job, and good luck!