Nice pictures at this link. They show instruments of flat stones,like xylophones, being struck to make music.
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.