Re: 2 things, one for you to try and the other is a Question.
Tap on the top of the guitar? I know the face of the guitar as the "top".
Given that, I get the sound of whatever chords I've got pressed regardless of which chord it is. The tapping makes the strings vibrate. They vibrate at the length permitted by your fingering (or lack thereof), producing the notes they're supposed to.
"Forced means you're painting a train blue." - Jets60
"If it comes from the heart and you add a few beers... it'll be awesome!" - Mekidsmom
"Don't ever apologize for what you have worked hard for." - Pete Benson
Official recipient of B chord amnesty.