The piano — an upright, the kind you see in the back of saloons in Western movies — had been gathering dust at the antique shop for years. It sounded like hell, and its price had been marked down repeatedly. The tag said $300 the day Sebastian Errazuriz saw it, which struck him as a bargain considering he had zero intention of playing the thing: He would buy it, load it into a van with his brother, then string it up from the double-height ceiling of his Brooklyn design studio as a “constant reminder of the possibility of death — a kind of personal Post-It.”