I agree with everything that was said so far (construction of the body, especially the hands, perspective, adding a bit of storytelling...) Another thing I think would improve the whole image is changing some of the violins in the back for other instruments. Right now it is extremely repetitive and I would vary it a bit with instruments of big-medium-small sizes to avoid the "ladder effect".
I have seen your introduction thread and you have improved tremendously is only 3 years! I hope this forum will help you as much as it is helping me.