That sure is a beautiful instrument: a wonderful place to start when aiming to create a beautiful image.
I'll start with what works for me in this shot. I like the point-of-view and the rich colour tones. The lighting is good, really bringing out the lines and flow of the sax.
I imagine the image was voted down a little because it does not absolutely 'pop' with gold. As has already been commented - it is dark and red. Personally I like the opulent hue and glow this gives to the shot, but others are different. Anyway, you have not been cut-down by the DNMC trolls - merely just marked down a bit.
I'm guessing the sax is at rest in it's case. It is a little too easy to see that the shot was rotated to veritcal. I think it would have worked better if you has set the sax in a stand with a slightly less dark background. This would have removed the distracting reflections in the inside of the bell.
I hope my comments help and Good Luck in future Challenges!