Pianoing help please

So ive decided to pick up a character that uses pianoing and I dont fully understand how to piano. when im comboing st mp into st mk into hands with gen I can clearly see the button presses of all 5 punches being pressed in the needed order but nothing comes out. also when pianoing are you continously pressing the button for instance lp,mp,hp would i treat that as me almost plinking lp and mp. and when performing pianoing do i need to keep my hand flat on my arcade stick for light presses or it doesnt matter the pressure i put on the buttons.

This link may help ya http://www.eventhubs.com/news/2010/nov/30/ssf4-piano-button-inputs-tutorial-vesper-arcade/