Updated through online information from Rick Erickson. -- The thunder machine was added later. The thunder machine, sheet is 2 x 6 ft of sheet metal. It was used each Good Friday for many years in the choir's performance of Dubois' Seven Last Words.
Information identifying this instrument from the Austin Organs, Inc. web site, accessed December 31, 2004: http://www.austinorgans.com/organ-research.htm.