Hi. Dragging the pencil randomly around works surprisingly well (I'm used to Logic, with its 12 tone scale), but I feel it should draw monophonically, i.e. not allow multiple notes in the same column. Not sure what other people think about that.
Yes, that's it. It can be tricky to implement properly. When making separate clicks, it should allow multiple simultaneous notes; and erasing should probably not behave like adding. But I realize this adds very little commercial interest to the product.