Pretty much the comments.
In all honesty, I can't think of a way to "improve" someone's music with a critique.
There are a lot of places where, let say:
You post a song on Soundcloud
Then allow the song to be listened by a music forum (I'm not sure where, exactly)
And allow them to tell you the details.
It's just up to finding a forum that would do that. And, I really don't know.
I'm deep within writing and music. And they both are the type of hobbies/jobs that you really can't have a outsider "take a look at" to help you. Especially for music when it's completely subjective, while writing is only partially subjective.
Truthfully, I've never heard someone say "I got help with this song" or something. Music is purely about defining a method and transpiring what you have in your head to that method. I can't see how someone's opinion would make your music better, when it is your music.