The Singing Metal Rib

My heavy forearms hauled me across the dusty concrete toward an enormous galvanized air duct running along the floor. Right on its flanged seam rested a long, discarded steel hacksaw blade, stripped of its frame. Heh heh... I planted my knuckle firmly over one end against the metal lip, using my claw to pull the flexible tip back into a tight curve. *Thwack-zzzzzt!* When I let go, the steel sprang back, buzzing violently against the hollow sheet-metal casing. The duct amplified the vibration into an eerie, buzzing groan that rumbled right through my chest. Leaning my head down close to the shuddering metal, I chuckled low into the vibration.