How to make professional-looking music videos on IPhone?

I have the IPhone4S and I was just trying to think of an app(s) that would make nice videos like Cimorelli has or mattybraps… I've tried Splice and Video Star. But there not really what I'm looking for. My friend and I make videos and we post them. But the thing is we want to do karoke, and Video Star you can't hear them, and splice is just terrible. How can I make good videos like Cimorelli, MattyBRaps?

Use imovie on app store