John Gordon has a knack for tinkering, so it isn’t surprising that when this retired resident of Groton found a large granite stone in his field, he decided to turn it into a calliope. You may have heard calliopes before at circuses and fairs. The musical instruments produce loud sounds by blowing gas, steam or compressed air through whistles. As far as John knows, this is the only calliope in the world made from a rock.