Personally I think Octavia should have her way with Sweetie Belle first: teach her the basic techniques and the classics until she has it down cold. Then DJ can get the little unicorn into freestyle/rap and working the crowd when Sweetie vocal talents are already second nature. But I can see the other side too. I'd love to see an "Epic Rap Battle of Equestria" between the young mares to decide who gets to tutor Sweetie Belle first.
It's a fun drawing overall, and though sparsely decorated I like the flourish of color above the main window then each's one wall hanging. Interesting layout and colors for the small place, but then again it could just be their practice room. Though the awards are on Octavia's side I suspect that they're actually Vinyl's just because they're microphones, but I won't over-think it. Too much.
Sweetie's shocked and confused face is perfect. Let's hope they don't rough her up too much with their tug-o-war.