I like the concept, composition and the way you've edited the colours of this piece. I actually don't think it's too dark - it highlights what you want the viewer to see well; the music notes and the pink hearts. The lighting also kind of looks dramatic - like a stage that has just been lit up for show. So I actually quite like it the way it is. I actually don't have any particularly useful suggestions for you except maybe experiment with the cropping but that's about it. Good luck!