Firstly, the composition of this is great- the 3 main subjects are spot on in focus and everything is very clean and sharp..great.
The use of colour is very effective here, the brass is beautiful and very rich and this really stands out against the monochrome-the saturation of the monochrome is spot on... I think I agree with JuliBoc- I would have prefered this if just the middle trumpet was coloured, I think this would have been more dramatic and add more meaning.
Jeffery, she looks so cute in this shot. I think the selective desat would have been more effective if you had left just your daughter's horn in color. Then the photo would have been about her playing the horn and not the horns.