Hold one in each hand and lightly tap them together. Not only will you avoid breaking the rocks by tapping them instead of hitting them, but the sound will be more pleasant to the ears. Then slowly introduce the other instruments, one by one. This will help the dramatic tension in your music build. The drum is a good instrument to start off with because you can establish a steady rhythm with it and base the rest of the music off the beat.
Rocks tend to make sounds that are harsh to the ear.
Try playing your instruments gently to make then sound better. Midway through your song, when three or more instruments are playing at the same time, stop playing all of the instruments except one. Then slowly introduce the other instruments back in. Click here to go to the test. Scientists believe Earth was formed 4,600 million years ago.