Gravestones could be keys on a keyboard

Nice pictures at this link. They show instruments of flat stones,like xylophones, being struck to make music.
http://www.atlasobscura.com/articles/the-mysterious-stone-instruments-that-keep-popping-up-in-vietnam

And to continue the article about "mysterious stone instruments", in a new direction:

Gravestones could be keys on a keyboard.

If so, that would not be original. SPEECH is the same thing. Because by the time the words are spoken, they refer to a past. There is no way to speak in the present tense--not "present" as in a current reality.