You should check the other projects of magenta, they did something like you describe with piano using 1400 training pieces. Now they only need user feedback to

You should check the other projects of magenta, they did something like you describe with piano using 1400 training pieces. Now they only need user feedback to find out which outputs of the network are garbage ... oh wait, maybe they are already doing that, who knows. Well, they are probably not tuning 100 instrument parameters but only the play characteristics like accent, velocity and so on.