ryjcio. I don't think you're a troll, nowehere near. But its not worth getting into an argument here, man. We are all here to learn - regardless of age, experience or how well we speak the Queen's English...
Onset to me is simply the way you start your note. Its vitally important because the way you start it will tend to be the way you end it, so if you start badly, it will be difficult to correct it.