Heat lightning screamed down from the sky. The mid-day August sun blasted Magazine Street in shimmering waves that seemed to ooze up from the pavement, but a few steps up from Napoleon the slate black former mortuary that houses Trent Reznor’s New Orleans studio was as cool and dark as the hidden cellars of Dr. Phibes. This musical tomb, walls lined with platinum records commemorating Reznor’s successes, was in the process of yielding its technic...