Dang. Do you mean to say that when I push a button, the metal itself vibrates in a certain frequency, thus creating the right tone? Any way you'd reckon I could bypass these oscillators?
The Wikipedia page you sent said:
Initial pushbutton designs employed levers, so that each button activated two contacts.
I think this is how my keypad works, the buttons themselves work as a wedge that pushes two pieces of metal strips to two contacts - one contact is connected to all the buttons in a row and the other to all the buttons in a column, this made me think that it would be as simple as using the Keypad.H library.